A free first person shooter for Mac, PC and Linux

Shoot and survive

Fast paced, first person strategy game

Source port for Build engine games

Free fast paced arena shooter

A Quake mod based on the retro shooter SPRAWL

A Zandronum 3.0 fork with improved netcode, configurable movement and many small tweaks

Yamagi Quake II is an alternative client for id Software's Quake II

First-person shooter with cooperative in-game map editing

Modern cross-platform port of the Descent engine

Open Source voxel shooter

Dhewm 3 is a Doom 3 GPL source port

The Free and Fast Arena Shooter

Tank digging battle game

a modern QuakeWorld client focused on competitive online play

Game engine for Classic Doom

A modernization effort of DOOM-3-BFG

Aliens vs Humans, First Person Shooter game with elements of Real Time Strategy

The orb ponderer's arena first-person shooter

Leading the way in newschool multiplayer Doom online

FPS aim trainer

Epic story-driven FPS running on the Build Engine

Classic arena first person shooter

Open source first person shooter

Free agile arena shooter

Game engine for Return to Castle Wolfenstein

ReC98 source port of the first Seihou Project game

EDuke32 is an awesome, free homebrew game engine

Open source first person shooter

A modern cross‑platform port of “STAR WARS™: Dark Forces” with mod support