Game engine for Classic Doom

Open Source voxel shooter

Source port for Build engine games

Shoot and survive

Leading the way in newschool multiplayer Doom online

Open source first person shooter

ReC98 source port of the first Seihou Project game

The Free and Fast Arena Shooter

dhewm 3 is a Doom 3 GPL source port

Epic story-driven FPS running on the Build Engine

A Quake mod based on the retro shooter SPRAWL

Top-down shooter action RPG

FPS aim trainer

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

First-person shooter game

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

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

Game engine for Return to Castle Wolfenstein

The orb ponderer's arena first-person shooter

Free fast paced arena shooter

a modern QuakeWorld client focused on competitive online play

Fast paced, first person strategy game

Free agile arena shooter

Classic arena first person shooter

A modernization effort of DOOM-3-BFG

Modern cross-platform port of the Descent engine

Tank digging battle game

First-person shooter with cooperative in-game map editing

Open source first person shooter

EDuke32 is an awesome, free homebrew game engine