Modern cross-platform port of the Descent engine

A modernization effort of DOOM-3-BFG

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

Source port for Build engine games

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

Epic story-driven FPS running on the Build Engine

Fast paced, first person strategy game

The Free and Fast Arena Shooter

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

EDuke32 is an awesome, free homebrew game engine

Open source first person shooter

Dhewm 3 is a Doom 3 GPL source port

Classic arena first person shooter

ReC98 source port of the first Seihou Project game

First-person shooter with cooperative in-game map editing

Top-down shooter action RPG

Open source first person shooter

Free fast paced arena shooter

Tank digging battle game

FPS aim trainer

Game engine for Classic Doom

The orb ponderer's arena first-person shooter

Game engine for Return to Castle Wolfenstein

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

Leading the way in newschool multiplayer Doom online

First-person shooter game

A Quake mod based on the retro shooter SPRAWL

a modern QuakeWorld client focused on competitive online play

Free agile arena shooter

Shoot and survive