Game engine for Return to Castle Wolfenstein

A modernization effort of DOOM-3-BFG

A Quake mod based on the retro shooter SPRAWL

First-person shooter with cooperative in-game map editing

Dhewm 3 is a Doom 3 GPL source port

Epic story-driven FPS running on the Build Engine

The orb ponderer's arena first-person shooter

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

Open source first person shooter

Open source first person shooter

Top-down shooter action RPG

EDuke32 is an awesome, free homebrew game engine

FPS aim trainer

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

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

Free fast paced arena shooter

The Free and Fast Arena Shooter

A free first person shooter for Mac, PC and Linux

Fast arcade first person shooter

Tank digging battle game

ReC98 source port of the first Seihou Project game

First-person shooter game

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

Free agile arena shooter

Classic arena first person shooter

a modern QuakeWorld client focused on competitive online play

Fast paced, first person strategy game

Leading the way in newschool multiplayer Doom online

Source port for Build engine games

Modern cross-platform port of the Descent engine