Tank digging battle game

Epic story-driven FPS running on the Build Engine

Classic arena first person shooter

Open source first person shooter

Top-down shooter action RPG

Open Source voxel shooter

The Free and Fast Arena Shooter

Free fast paced arena shooter

Game engine for Return to Castle Wolfenstein

Open Source voxel shooter

Free agile arena shooter

Game engine for Classic Doom

A modernization effort of DOOM-3-BFG

Shoot and survive

Fast paced, first person strategy game

First-person shooter with cooperative in-game map editing

The orb ponderer's arena first-person shooter

Leading the way in newschool multiplayer Doom online

A Quake mod based on the retro shooter SPRAWL

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

Modern cross-platform port of the Descent engine

FPS aim trainer

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

Open source first person shooter

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

First-person shooter game

a modern QuakeWorld client focused on competitive online play

A free first person shooter for Mac, PC and Linux

EDuke32 is an awesome, free homebrew game engine

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