Open source first person shooter

Game engine for Classic Doom

Free agile arena shooter

Source port for Build engine games

FPS aim trainer

Open Source voxel shooter

Open source first person shooter

First-person shooter game

Fast paced, first person strategy game

Free fast paced arena shooter

EDuke32 is an awesome, free homebrew game engine

The Free and Fast Arena Shooter

Game engine for Return to Castle Wolfenstein

Open Source voxel shooter

The orb ponderer's arena first-person shooter

Tank digging battle game

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

Shoot and survive

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

ReC98 source port of the first Seihou Project game

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

Epic story-driven FPS running on the Build Engine

Top-down shooter action RPG

A modernization effort of DOOM-3-BFG

Fast arcade first person shooter

Classic arena first person shooter

First-person shooter with cooperative in-game map editing

a modern QuakeWorld client focused on competitive online play

Modern cross-platform port of the Descent engine

A Quake mod based on the retro shooter SPRAWL