A free first person shooter for Mac, PC and Linux

First-person shooter game

ReC98 source port of the first Seihou Project 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

Open Source voxel shooter

Leading the way in newschool multiplayer Doom online

The Free and Fast Arena Shooter

Source port for Build engine games

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

Classic arena first person shooter

A Doom II mod with weapons and mechanics inspired by Quake Champions

Dhewm 3 is a Doom 3 GPL source port

Modern cross-platform port of the Descent engine

Top-down shooter action RPG

The orb ponderer's arena first-person shooter

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

Fast paced, first person strategy game

a modern QuakeWorld client focused on competitive online play

Free agile arena shooter

A modernization effort of DOOM-3-BFG

Fast arcade first person shooter

Tank digging battle game

FPS aim trainer

Epic story-driven FPS running on the Build Engine

EDuke32 is an awesome, free homebrew game engine

Free fast paced arena shooter

Game engine for Return to Castle Wolfenstein

First-person shooter with cooperative in-game map editing

Open source first person shooter