A free first person shooter for Mac, PC and Linux

Fast arcade first person shooter

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

Classic arena first person shooter

Free agile arena shooter

Game engine for Classic Doom

A modernization effort of DOOM-3-BFG

The Free and Fast Arena Shooter

Game engine for Return to Castle Wolfenstein

Dhewm 3 is a Doom 3 GPL source port

Top-down shooter action RPG

First-person shooter with cooperative in-game map editing

EDuke32 is an awesome, free homebrew game engine

A Quake mod based on the retro shooter SPRAWL

The orb ponderer's arena first-person shooter

Modern cross-platform port of the Descent engine

First-person shooter game

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

Tank digging battle game

Shoot and survive

ReC98 source port of the first Seihou Project game

Open Source voxel shooter

Source port for Build engine games

Open source first person shooter

Epic story-driven FPS running on the Build Engine

Free fast paced arena shooter

FPS aim trainer

a modern QuakeWorld client focused on competitive online play

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

Open source first person shooter