The 180 Best Security & Privacy in 2026

ExpressVPN

Fast, easy-to-use VPN with a large server network.

Paid (Subscription)

Best for: Casual users seeking ease and streaming support

Bitwarden

Open-source password manager with a generous free tier.

Freemium

Best for: Budget-conscious security enthusiasts

Proton VPN

Privacy-focused VPN from the makers of Proton Mail.

Freemium

Best for: Privacy enthusiasts on a budget

Signal

Private, end-to-end encrypted messaging.

Free

Best for: Privacy-conscious individuals

1Password

A secure password manager and digital vault.

Paid (Subscription)

Best for: Individuals and families seeking strong password security.

Dashlane

Password manager with proactive security tools.

Freemium

Best for: Individuals seeking comprehensive security tools

NordVPN

A fast, secure VPN with a large global server network.

Paid (Subscription)

Best for: Remote workers and serious privacy enthusiasts

Surfshark

Budget-friendly VPN with unlimited devices.

Paid (Subscription)

Best for: Large families on a budget

RoboForm

Password manager and form filler that saves logins and completes forms automatically

Freemium

Best for: Users who want strong autofill for both passwords and complex web forms from a long-established vendor.

AxCrypt

AES-256 file encryption with secure sharing for individuals and teams

Paid (Subscription)

Best for: Individuals or teams who want simple AES-256 file encryption integrated with existing cloud storage

SailPoint

Enterprise identity security platform that governs access for human and machine identities.

Contact for Pricing

Best for: Large, regulated enterprises that need formal access certification and compliance-grade identity governance.

Frontegg

Identity layer for SaaS applications, covering login, SSO, and agentic access.

Freemium

Best for: B2B SaaS teams that need multi-tenant login, SSO, and SCIM without building identity infrastructure in-house.

AVG AntiVirus

Antivirus and internet security suite with free and paid tiers for real-time malware and scam protection.

Freemium

Best for: Home users who want a free baseline antivirus with the option to add firewall, VPN, and PC cleanup later.

Cryptomator

Open-source client-side encryption that locks individual files before they sync to any cloud drive.

Freemium

Best for: Anyone who wants to keep using Dropbox, Google Drive, or OneDrive but encrypt files locally first.

velociraptor

Digital Forensics and Incident Response

Free

Best for: Experienced DFIR teams seeking automation and scalability.

OpenSSL

General purpose TLS and crypto library

Free

Best for: Experienced developers and security professionals

Mobile-Security-Framework-MobSF

Automated mobile app security testing and analysis framework

Free

Best for: Experienced security professionals and developers

logto

Modern authentication and authorization infrastructure for developers

Freemium

Best for: SaaS founders and developers needing scalable auth solutions

better-auth

Comprehensive authentication framework

Free

Best for: Enterprise developers needing secure authentication solutions

AuthPass

Cross-platform password manager compatible with Keepass 2.x

Free

Best for: Small teams and Keepass users

gokey

Simple vaultless password manager in Go

Free

Best for: DevOps teams and developers seeking simple security solutions

Xray-core

An open platform for various uses

Free

Best for: Advanced developers and power users

Norton Antivirus

Real-time virus protection with identity-theft safeguards for multiple devices

Paid (Subscription)

Best for: Multi-device households and small businesses

ClamAV

Open-source antivirus engine for detecting malware across platforms

Free

Best for: Sysadmins needing free, cross‑platform malware scanning with CLI integration

Metasploit

Widely used open-source penetration testing framework for finding and exploiting vulnerabilities.

Freemium

Best for: Security professionals who need a free, extensible exploit and pentesting framework.

nodewarden

Bitwarden‑compatible vault hosted on Cloudflare Workers for free

Free

Best for: Tech‑savvy self‑hosters with a Cloudflare account

CyberGhost VPN

VPN with 11,000+ servers in 100 countries plus dedicated streaming and gaming servers.

Paid (Subscription)

Best for: Users who want a large, streaming-optimized server network with an easy one-click app.

Trend Micro Apex One

AI-driven endpoint protection that stops threats before they strike

Paid (Subscription)

Best for: Enterprises and midsize firms needing AI‑driven, cloud‑managed endpoint security

Panda Dome

Panda Security's next-gen antivirus suite for Windows, Mac, Android, and iOS.

Freemium

Best for: Home users wanting an affordable antivirus suite with Dark Web monitoring and VPN included.

McAfee

AI-powered antivirus with identity theft, scam, and privacy protection for PCs and phones.

Paid (Subscription)

Best for: Households wanting one subscription that bundles antivirus, VPN, and identity monitoring.

BestCrypt Container Encryption

Cross-platform encrypted containers from Jetico for protecting files on disk and in cloud storage.

Contact for Pricing

Best for: Users who sync sensitive files through Dropbox or similar services and want them encrypted before upload.

TorGuard

Anonymous VPN and stealth proxy service with WireGuard, dedicated IPs, and V2Ray obfuscation.

Paid (Subscription)

Best for: Users who need obfuscated stealth VPN protocols to bypass strict firewalls or VPN blocks.

VeePN

VPN bundled with real-time antivirus, breach alerts, and identity protection tools.

Paid (Subscription)

Best for: Budget-conscious users wanting VPN, antivirus, and breach monitoring in one bundled subscription

passbolt_api

Open source password manager for teams

Free

Best for: Large teams and organizations

prowler

Automate cloud security and compliance

Free

Best for: Tech-savvy cloud security teams

osquery

Open-source SQL framework for querying and auditing Linux, Windows, and macOS endpoints.

Free

Best for: Security and DevOps teams that want SQL-based, open-source endpoint visibility they can build fleet tooling around.

Password Boss

Password management built for MSPs to secure and manage client credentials at scale.

Contact for Pricing

Best for: MSPs that need one place to manage and audit passwords across many client accounts alongside RMM tools.

SafeLine

Self-hosted WAF and reverse proxy for web app protection

Freemium

Best for: Experienced web developers and administrators

GnuPG

Free, complete implementation of the OpenPGP standard for encrypting and signing data.

Free

Best for: Technical users who want a free, auditable, open-source OpenPGP implementation for encryption and signing.

SonicWall

Next-generation firewall appliances with real-time deep packet inspection for businesses of all sizes.

Contact for Pricing

Best for: Businesses wanting a range of firewall appliance sizes with an embedded cyber warranty.

Authy

Twilio's two-factor authentication app with secure cloud backup and multi-device sync.

Free

Best for: People who want a free, simple mobile 2FA app with encrypted cross-device backup.

Yubico Authenticator

Companion app that generates 2FA codes stored securely on a physical YubiKey.

Free

Best for: YubiKey owners who want their 2FA codes stored on hardware instead of their phone.

JumpCloud

Cloud directory platform unifying single sign-on, MFA, and device management for hybrid workforces.

Paid (Subscription)

Best for: IT teams wanting directory, SSO, MFA, and device management from one cloud console instead of stitching tools together.

IPFire

Free, open-source Linux firewall distribution with intrusion prevention and built-in VPN.

Free

Best for: Technical users who want a free, self-hosted firewall with built-in IPS and VPN.

IPVanish

Unlimited-device VPN built for streaming, torrenting, and Fire TV/Android TV setups

Paid (Subscription)

Best for: Households needing unlimited-device VPN coverage with strong Fire TV/Firestick streaming support

OPNsense

Open-source, FreeBSD-based firewall and routing platform with a free core and paid Business Edition.

Freemium

Best for: Admins who want an open-source, feature-rich firewall/router they fully control.

crowdsec

Open-source, crowdsourced security engine that blocks malicious IPs in real time

Freemium

Best for: Sysadmins/DevOps needing free, community‑driven IP blocking

Windscribe

VPN with a generous free tier and built-in ad, tracker, and malware blocking.

Freemium

Best for: Users wanting a genuinely usable free VPN tier plus optional low-cost, location-specific paid plans

VeraCrypt

Free open-source disk encryption with strong security, successor to TrueCrypt.

Free

Best for: Users who want free, auditable, strong disk and file encryption without any subscription.

miniOrange

Identity and access management suite covering SSO, MFA, PAM, and identity governance.

Paid (Subscription)

Best for: Organizations wanting one vendor for SSO, MFA, PAM, and MDM with transparent starter pricing.

Ping Identity

Enterprise identity platform combining SSO, MFA, and adaptive authentication.

Contact for Pricing

Best for: Enterprises needing a single platform for workforce, customer, and B2B identity with strong adaptive authentication.

keycloak

Open-source identity and access management for modern applications

Free

Best for: Enterprises and dev teams needing free, standards‑compliant SSO with custom extensions

FusionAuth

Developer-friendly identity and access management platform

Freemium

Best for: Dev teams needing a free, self‑hostable IAM with extensive SDKs

john

Advanced offline password cracker supporting hundreds of hash types

Free

Best for: Security auditors needing high‑performance, customizable offline hash cracking

Malwarebytes

Detects and removes advanced threats and malware

Paid (Subscription)

Best for: Home users and small businesses

Magic Lasso Adblock

Independent ad and tracker blocker for Safari and apps on Apple devices

Paid (Subscription)

Best for: Apple users who want independent ad blocking that also covers non-Safari apps

NordLocker

Zero-knowledge encrypted cloud storage from the makers of NordVPN

Freemium

Best for: Privacy-focused users who want zero-knowledge encrypted cloud storage from an established security company

mitmproxy

Interactive, scriptable man‑in‑the‑middle proxy for HTTP, HTTPS and WebSocket traffic

Free

Best for: Security researchers needing deep, scriptable traffic manipulation

Padloc

Secure password manager with zero‑knowledge encryption for individuals and teams

Freemium

Best for: Teams needing secure shared vaults with zero‑knowledge encryption

Twingate

Zero-trust remote access to private networks and apps without a traditional VPN

Freemium

Best for: Distributed teams that want VPN-level security with app-level access control and minimal latency.

Authelia

Single Sign-On Multi-Factor portal for web apps

Free

Best for: DevOps teams seeking scalable authentication solutions

Kali Linux 2023.3

The latest Kali Linux release with updated tools for penetration testing and security research.

Free

Best for: Penetration testers and security researchers needing latest open‑source toolset

Wazuh

Unified XDR and SIEM protection for endpoints and cloud workloads

Free

Best for: Large-scale enterprise security teams

KeeWeb

Free, open-source password manager

Free

Best for: Small teams and individuals on a budget

Zscaler Internet Access

Secure, fast internet and SaaS access for any user, any device.

Paid (Subscription)

Best for: Enterprises and mid‑market firms needing cloud‑native, globally‑scalable secure web gateway

CrowdStrike Falcon

AI‑driven endpoint protection that stops breaches in real time

Best for: Large enterprises needing AI‑driven, cloud‑native endpoint protection

Intruder

Cloud-based exposure management platform for continuous vulnerability scanning.

Contact for Pricing

Best for: Security teams that want continuous, automated vulnerability and cloud misconfiguration scanning in one dashboard.

blocky

Fast and lightweight DNS proxy as ad-blocker for local network

Free

Best for: Small networks seeking simple ad-blocking

VyprVPN

Independently audited no-log VPN with a proprietary DNS service.

Paid (Subscription)

Best for: Users who want a VPN with an independently audited no-log claim and its own DNS infrastructure.

Virtru

Data-centric encryption and access control for email, files, and SaaS apps.

Contact for Pricing

Best for: Regulated organizations that need to keep control over sensitive data even after it's shared externally.

Astrill VPN

VPN service built around a proprietary StealthVPN protocol to defeat censorship.

Paid (Subscription)

Best for: Users in heavily censored regions who need a stealth protocol specifically engineered to beat deep packet inspection.

SpiderFoot

Automate OSINT for threat intelligence and attack surface mapping

Free

Best for: Large organizations with in-house security teams

WireGuard

Fast, simple, and modern VPN for secure networking

Free

Best for: Enterprises and dev teams needing high‑speed, auditable VPNs

Proton Pass

Secure, encrypted password manager built for privacy‑first users.

Freemium

Best for: Privacy‑focused individuals and small teams needing encrypted password sync

Endian

Integrated IT and OT security gateway platform for business and industrial networks.

Contact for Pricing

Best for: Manufacturers and critical infrastructure operators needing one platform to secure both IT and industrial OT networks.

Clerk

Instant auth and user management with prebuilt UI components

Freemium

Best for: Web developers needing quick, secure auth with prebuilt UI components

LastPass

Securely store and generate passwords

Freemium

Best for: Individuals seeking secure password storage

Mullvad VPN

Secure, private, and anonymous internet browsing without personal info

Paid (Subscription)

Best for: Privacy-conscious individuals

Cryptee

End-to-end encrypted cloud storage for private notes, documents, and photos

Freemium

Best for: Privacy-focused users who want end-to-end encrypted notes and photo storage with no tracking.

Descope

No-code CIAM platform for building authentication flows for users, partners, and AI agents.

Freemium

Best for: Product teams wanting a no-code way to add passwordless auth, SSO, and fine-grained authorization to their app.

Detectify

Application security platform combining payload-based scanning with ethical hacker research.

Contact for Pricing

Best for: AppSec teams that want fast-moving vulnerability coverage backed by real ethical hacker research, not just static scans.

Kaspersky Premium

Comprehensive protection for your digital life (formerly Kaspersky Total Security)

Paid (Subscription)

Best for: Home users with multiple devices

Socket

Supply chain security platform that flags malicious and risky open-source dependencies.

Freemium

Best for: Engineering teams wanting automated, low-noise scanning for malicious or risky open-source dependencies in CI/CD.

Deep Freeze

Reboot to restore your PC, Mac, or server to a pristine state.

Paid (One-time)

Best for: Enterprises or schools with shared Windows/macOS PCs needing instant reboot restore

WorkOS

Enterprise-ready auth, SSO and SCIM APIs for B2B SaaS

Freemium

Best for: B2B SaaS teams needing rapid, enterprise‑grade auth and SSO integration

Tails OS

A portable OS that preserves your privacy and anonymity

Free

Best for: Activists, journalists, and whistleblowers needing portable, Tor‑only anonymity

shhgit

Secrets detection for GitHub, GitLab and Bitbucket repositories

Free

Best for: Small dev teams and open-source projects

NordLayer

Cloud-native business VPN and network security platform from Nord Security.

Paid (Subscription)

Best for: Businesses that need per-seat VPN, Zero Trust access, and threat prevention without deploying hardware.

Palo Alto Networks Panorama

Centralized management for Palo Alto firewalls and Prisma Access.

Paid (Subscription)

Best for: Enterprises or MSSPs managing multiple Palo Alto firewalls

AdGuard Home

Network-wide ads & trackers blocking DNS server

Free

Best for: Small businesses and tech-savvy home users

Snyk

Secure code by finding and fixing open-source, container and IaC vulnerabilities.

Freemium

Best for: Dev teams needing automated vulnerability fixes in CI pipelines

Avast Antivirus

Free-tier malware protection with Wi-Fi scanning and a file shredder

Freemium

Best for: Home users seeking comprehensive security

Auth0

Developer-focused identity platform for authentication and authorization

Paid (Subscription)

Best for: Large-scale enterprise applications

hiddify-app

Auto-proxy client

Free

Best for: Power users seeking secure browsing

Drata

Automate security compliance and reduce audit prep work

Paid (Subscription)

Best for: Mid-sized businesses with standard compliance needs

connaisseur

Kubernetes admission controller for container image signature verification

Free

Best for: Kubernetes admins seeking robust image security

Aegis

Free open-source Android app for secure 2-step verification tokens.

Free

Best for: Android users who want a free, open-source 2FA app with local encryption

Teleport

Secure access to all infrastructure

Freemium

Best for: Large teams and enterprise infrastructure management

Keeper Security

Zero-knowledge password manager and privileged access platform for individuals, families, and enterprises.

Paid (Subscription)

Best for: Organizations that want password management and privileged access management under one zero-knowledge platform.

CyberChef

The web app for all your data manipulation and decoding needs

Free

Best for: Security analysts needing quick, shareable browser‑based data transforms

pfSense

Open-source firewall, router, and VPN platform trusted by enterprises for network security.

Freemium

Best for: Technical teams wanting a free, enterprise-capable firewall/router/VPN platform they can self-host or run in the cloud.

Tailscale

Easy, secure WireGuard networking with 2FA

Freemium

Best for: Small to medium-sized remote teams

Tenable Nessus

Vulnerability assessment scanner that finds, prioritizes, and helps remediate security weaknesses.

Paid (Subscription)

Best for: Security teams needing a trusted, actively updated vulnerability scanner with strong risk prioritization.

KeePass2Android

Secure password management on Android

Free

Best for: Individuals seeking simple Android password management

Bitdefender Total Security

Multi-layered threat detection with secure banking and anti-ransomware

Paid (Subscription)

Best for: Small businesses and families with multiple devices

MacPass

Password management for macOS

Free

Best for: Casual macOS users seeking basic security

OpenVPN Access Server

Self‑hosted VPN solution with web UI and client support

Freemium

Best for: Small to midsize teams needing a self‑hosted VPN with web UI

gopass

A secure password manager for teams

Free

Best for: DevOps teams

unleashed-firmware

Stable custom firmware for Flipper Zero with advanced features

Free

Best for: Experienced hackers and makers

syft

Generate Software Bill of Materials from container images and filesystems

Free

Best for: DevOps and security teams needing free, comprehensive SBOMs for containers

Forcepoint DLP

Prevent data loss everywhere with precise classification and enforcement.

Best for: Large enterprises and regulated industries needing enterprise‑wide DLP

AliasVault

Secure password vault built for teams, with instant sharing and audit trails.

Free

Best for: Mid‑size teams needing audit‑ready password sharing

FlClash

Open-source, ad‑free ClashMeta proxy client for all major platforms

Freemium

Best for: Cross‑platform users seeking an open‑source, ad‑free ClashMeta client

v2rayNG

Open‑source V2Ray client for Android, giving power users full proxy control

Free

Best for: Power users and developers needing granular V2Ray proxy control on Android

KeePassXC

A modern, secure password manager

Free

Best for: Tech-savvy individuals

Emsisoft

Dual-engine anti-malware and endpoint protection built for small and midsize businesses.

Paid (Subscription)

Best for: Small businesses and MSPs wanting dual-engine, behavior-based ransomware protection with centralized management.

Privacy Badger

Free browser extension from EFF that learns to block hidden trackers as you browse.

Free

Best for: Anyone who wants free, automatic tracker blocking from a trusted nonprofit without managing filter lists.

ZoneAlarm

AI-powered firewall and antivirus suite from Check Point for Windows, Mac, and mobile.

Freemium

Best for: Home users who want a free two-way firewall with the option to add antivirus and ransomware protection from the same vendor.

Cloudflare WARP

Secure, fast internet with Cloudflare’s free VPN‑like service

Freemium

Best for: Consumers and small businesses seeking easy, free privacy and faster browsing

Vanta

Automated security compliance monitoring and evidence collection.

Paid (Subscription)

Best for: Mid‑size SaaS firms needing continuous SOC 2/ISO compliance

pi-hole

Network-wide ad blocking DNS server for homes and small businesses

Free

Best for: Tech-savvy home users

Have I Been Pwned

Check if your email address or password has surfaced in a known data breach.

Freemium

Best for: Anyone wanting a fast, free check of whether an email or password has leaked in a known breach.

Sherlock

Find social media profiles by username

Free

Best for: Researchers and casual investigators

v2rayN

GUI client for Xray, sing-box and others

Free

Best for: Advanced users seeking customizable VPN solutions.

GPG Suite

Mac toolset that brings OpenPGP encryption, key management, and Mail integration to macOS.

Freemium

Best for: Mac users who want native OpenPGP encryption with optional Apple Mail integration.

OWASP ZAP

Free, open-source web app security scanner stewarded by Checkmarx.

Free

Best for: Teams wanting a free, extensible DAST scanner that fits both manual pentesting and CI/CD automation.

hide.me

No-log VPN with a genuine free tier and apps for desktop, mobile, and browsers.

Freemium

Best for: Users who want a genuinely free, unlimited-data VPN tier with the option to upgrade for more locations.

Burp Suite

Web application penetration testing toolkit from PortSwigger.

Freemium

Best for: Security professionals who need a proven manual and automated web app testing toolkit.

tpotce

The all-in-one multi honeypot platform for comprehensive network defense.

Free

Best for: Experienced security teams with dedicated resources

dirsearch

Discover hidden web server directories and resources

Free

Best for: Experienced security professionals and penetration testers

strix

Open-source AI penetration testing tool to find and fix vulnerabilities.

Free

Best for: Tech-savvy security teams and developers

Semgrep

Find security bugs fast with customizable pattern‑matching rules

Freemium

Best for: Teams needing fast, customizable static analysis across multiple languages

TunnelBear

Secure and private browsing with a user-friendly VPN

Freemium

Best for: Casual VPN users and small teams

OpenSnitch

Interactive application firewall for GNU/Linux

Free

Best for: Linux security enthusiasts

Okta

Enterprise identity and access management platform

Best for: Large enterprises with complex access needs

Wiz

Cloud security platform for multi-cloud infrastructure

Paid (Subscription)

Best for: Cloud-native orgs with multi-cloud infrastructure

SuperTokens

Open-source authentication solution for secure user management

Free

Best for: Developers with authentication experience

Folder Lock

Windows file, folder, and drive encryption with cloud backup and file shredding.

Freemium

Best for: Windows users who want simple file/folder encryption with a one-time license instead of a subscription.

lesspass

Stateless password manager

Free

Best for: Tech-savvy security enthusiasts

Private Internet Access

No-logs VPN with open-source apps, unlimited connections, and strong torrenting support.

Paid (Subscription)

Best for: Torrent/P2P users and privacy purists who want an independently audited, open-source no-logs VPN

ESET PROTECT

ESET's cloud-first, AI-native cybersecurity platform for business endpoint protection.

Contact for Pricing

Best for: Businesses wanting a single console for endpoint, mail, and cloud security with strong lab-tested detection.

Sophos Firewall

Next-generation firewall with synchronized security and AI-powered threat detection for SMBs and enterprises.

Contact for Pricing

Best for: Organizations already using Sophos endpoint or email security wanting synchronized network protection.

Greenbone (OpenVAS)

Vulnerability management platform behind the widely used OpenVAS scanning engine, from appliance to free edition.

Freemium

Best for: Teams wanting a free, open-source vulnerability scanner with an option to scale to an enterprise appliance.

IVPN

No-logs VPN from a 15-year operator that publishes transparency reports and annual security audits.

Paid (Subscription)

Best for: Users who want a VPN with independently audited, publicly documented no-logs claims.

Check Point Next Generation Firewall

Unified security gateway with threat prevention and zero‑trust controls

Paid (Subscription)

Best for: Enterprises or midsize orgs needing integrated threat‑prevention and zero‑trust

PassGenZ

Instantly generate strong, secure and memorable passwords online.

Free

Best for: Users who need instant, free, browser‑based strong passwords

authentik

The authentication glue you need

Free

Best for: Large-scale, complex identity management projects

KeePassDX

Secure password management for Android

Free

Best for: Android users seeking free password security

GoodAccess

Cloud-based Zero Trust business VPN for securing remote teams without hardware

Paid (Subscription)

Best for: SMEs that need compliance-ready remote access security without hiring a networking team.

UpGuard

Cyber risk platform for vendor risk, attack surface, and third-party security monitoring

Contact for Pricing

Best for: Security teams that need continuous visibility into vendor risk and external attack surface.

Secureframe

Compliance automation for security certifications

Contact for Pricing

Best for: Mid-sized businesses seeking SOC 2 compliance

ghidra

Software reverse engineering framework

Free

Best for: Advanced security researchers and developers

Cisco Umbrella

Cloud‑delivered DNS security that blocks threats before they reach users

Paid (Subscription)

Best for: Large enterprises and distributed teams needing cloud DNS/web gateway protection

lynis

Security auditing and system hardening tool

Free

Best for: Experienced system administrators and security professionals

SentinelOne

Autonomous AI‑driven endpoint protection and response

Best for: Enterprises and mid‑size firms needing AI‑driven, automated endpoint protection

Total Adblock

Ad and tracker blocking browser extension and mobile app for cleaner, faster browsing

Paid (Subscription)

Best for: Users who want one paid subscription covering ad blocking on both desktop browsers and mobile devices.

Portmaster

Free, open-source application firewall with system-wide tracker and ad blocking

Freemium

Best for: Privacy-focused Windows and Linux users who want free, open-source, per-application network control.

Little Snitch

See and control every outgoing connection on your Mac with this application firewall.

Paid (One-time)

Best for: Mac users who want full visibility and control over which apps talk to the internet.

OneLogin

Cloud-based single sign-on and identity management for workforce and customer apps.

Contact for Pricing

Best for: Mid-size to large organizations wanting mature SSO plus MFA under the One Identity umbrella.

Stytch

Passwordless authentication, SSO, and fraud protection APIs for developers

Freemium

Best for: Dev teams building passwordless login with built‑in fraud protection

x64dbg

Powerful open‑source debugger for Windows reverse engineering

Free

Best for: Seasoned Windows reverse engineers needing extensible debugging