First-person shooter game

Free agile arena shooter

ReC98 source port of the first Seihou Project game

Fast paced, first person strategy game

Classic arena first person shooter

Free fast paced arena shooter

Tank digging battle game

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

Game engine for Return to Castle Wolfenstein

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

FPS aim trainer

Leading the way in newschool multiplayer Doom online

Top-down shooter action RPG

The orb ponderer's arena first-person shooter

The Free and Fast Arena Shooter

Source port for Build engine games

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

dhewm 3 is a Doom 3 GPL source port

A Quake mod based on the retro shooter SPRAWL

Shoot and survive

Open source first person shooter

a modern QuakeWorld client focused on competitive online play

Game engine for Classic Doom

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

Open Source voxel shooter

A modernization effort of DOOM-3-BFG

Open source first person shooter

Epic story-driven FPS running on the Build Engine

EDuke32 is an awesome, free homebrew game engine

Modern cross-platform port of the Descent engine