Fast arcade first person shooter

A free first person shooter for Mac, PC and Linux

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

Game engine for Return to Castle Wolfenstein

A modernization effort of DOOM-3-BFG

The Free and Fast Arena Shooter

Free agile arena shooter

First-person shooter with cooperative in-game map editing

A Quake mod based on the retro shooter SPRAWL

Top-down shooter action RPG

Dhewm 3 is a Doom 3 GPL source port

Classic arena first person shooter

The orb ponderer's arena first-person shooter

FPS aim trainer

Free fast paced arena shooter

a modern QuakeWorld client focused on competitive online play

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

Tank digging battle game

Open source first person shooter

First-person shooter game

EDuke32 is an awesome, free homebrew game engine

Game engine for Classic Doom

Modern cross-platform port of the Descent engine

ReC98 source port of the first Seihou Project game

Epic story-driven FPS running on the Build Engine

Open source first person shooter

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

Open Source voxel shooter

Shoot and survive

Source port for Build engine games