Shoot and survive

Open source first person shooter

The Free and Fast Arena Shooter

ReC98 source port of the first Seihou Project game

Source port for Build engine games

First-person shooter game

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

Classic arena first person shooter

Game engine for Return to Castle Wolfenstein

Free fast paced arena shooter

Open Source voxel shooter

Game engine for Classic Doom

FPS aim trainer

EDuke32 is an awesome, free homebrew game engine

Tank digging battle game

Free agile arena shooter

Leading the way in newschool multiplayer Doom online

Fast paced, first person strategy game

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

Top-down shooter action RPG

Epic story-driven FPS running on the Build Engine

Open source first person shooter

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

A modernization effort of DOOM-3-BFG

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

dhewm 3 is a Doom 3 GPL source port

Modern cross-platform port of the Descent engine

First-person shooter with cooperative in-game map editing

The orb ponderer's arena first-person shooter

a modern QuakeWorld client focused on competitive online play