A free first person shooter for Mac, PC and Linux

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

Free agile arena shooter

Tank digging battle game

Open Source voxel shooter

Open source first person shooter

Shoot and survive

First-person shooter game

Open source first person shooter

Epic story-driven FPS running on the Build Engine

FPS aim trainer

Classic arena first person shooter

Game engine for Classic Doom

The Free and Fast Arena Shooter

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

Game engine for Return to Castle Wolfenstein

ReC98 source port of the first Seihou Project game

Leading the way in newschool multiplayer Doom online

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

First-person shooter with cooperative in-game map editing

EDuke32 is an awesome, free homebrew game engine

Dhewm 3 is a Doom 3 GPL source port

Top-down shooter action RPG

Free fast paced arena shooter

Source port for Build engine games

Modern cross-platform port of the Descent engine

A modernization effort of DOOM-3-BFG

A Quake mod based on the retro shooter SPRAWL

Fast paced, first person strategy game

The orb ponderer's arena first-person shooter