Fast paced, first person strategy game

Tank digging battle game

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

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

A free first person shooter for Mac, PC and Linux

A Quake mod based on the retro shooter SPRAWL

Top-down shooter action RPG

Game engine for Classic Doom

Classic arena first person shooter

Game engine for Return to Castle Wolfenstein

Modern cross-platform port of the Descent engine

Shoot and survive

Free fast paced arena shooter

Source port for Build engine games

Open source first person shooter

The Free and Fast Arena Shooter

FPS aim trainer

Open Source voxel shooter

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

Epic story-driven FPS running on the Build Engine

Free agile arena shooter

Dhewm 3 is a Doom 3 GPL source port

EDuke32 is an awesome, free homebrew game engine

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

A modernization effort of DOOM-3-BFG

Open source first person shooter

Leading the way in newschool multiplayer Doom online

First-person shooter game

First-person shooter with cooperative in-game map editing

ReC98 source port of the first Seihou Project game