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

dhewm 3 is a Doom 3 GPL source port

A Quake mod based on the retro shooter SPRAWL

Epic story-driven FPS running on the Build Engine

ReC98 source port of the first Seihou Project game

Classic arena first person shooter

Modern cross-platform port of the Descent engine

A modernization effort of DOOM-3-BFG

Fast paced, first person strategy game

The orb ponderer's arena first-person shooter

Open source first person shooter

Free agile arena shooter

Free fast paced arena shooter

The Free and Fast Arena Shooter

Shoot and survive

First-person shooter game

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

Leading the way in newschool multiplayer Doom online

EDuke32 is an awesome, free homebrew game engine

FPS aim trainer

a modern QuakeWorld client focused on competitive online play

Top-down shooter action RPG

Tank digging battle game

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

Open Source voxel shooter

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

Game engine for Classic Doom

Open source first person shooter

First-person shooter with cooperative in-game map editing

Source port for Build engine games