The orb ponderer's arena first-person shooter

Open Source voxel shooter

Modern cross-platform port of the Descent engine

Leading the way in newschool multiplayer Doom online

Shoot and survive

Epic story-driven FPS running on the Build Engine

Tank digging battle game

FPS aim trainer

Dhewm 3 is a Doom 3 GPL source port

Classic arena first person shooter

Open source first person shooter

ReC98 source port of the first Seihou Project game

Game engine for Return to Castle Wolfenstein

The Free and Fast Arena Shooter

Game engine for Classic Doom

a modern QuakeWorld client focused on competitive online play

Free fast paced arena shooter

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

Source port for Build engine games

EDuke32 is an awesome, free homebrew game engine

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

First-person shooter game

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

A modernization effort of DOOM-3-BFG

Fast paced, first person strategy game

First-person shooter with cooperative in-game map editing

Top-down shooter action RPG

Free agile arena shooter

Open source first person shooter

A Quake mod based on the retro shooter SPRAWL