A modernization effort of DOOM-3-BFG

Modern cross-platform port of the Descent engine

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

Fast paced, first person strategy game

Open source first person shooter

ReC98 source port of the first Seihou Project game

Free fast paced arena shooter

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

Source port for Build engine games

EDuke32 is an awesome, free homebrew game engine

Free agile arena shooter

Dhewm 3 is a Doom 3 GPL source port

Tank digging battle game

The Free and Fast Arena Shooter

FPS aim trainer

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

Game engine for Return to Castle Wolfenstein

A Quake mod based on the retro shooter SPRAWL

The orb ponderer's arena first-person shooter

Open source first person shooter

First-person shooter game

Epic story-driven FPS running on the Build Engine

Classic arena first person shooter

Shoot and survive

Top-down shooter action RPG

Open Source voxel shooter

a modern QuakeWorld client focused on competitive online play

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

A free first person shooter for Mac, PC and Linux

First-person shooter with cooperative in-game map editing