Warsow is a free standalone first person shooter game for Windows and Linux. It is based on the Qfusion 3D engine (a modification of the Quake 2 GPL engine), and aimed on the competitive scene, or the e-sports community.

Do you like fast paced deathmatch? How about rich, colorful, arcadelike atmospheres?

World of Padman (WoP) is an open source first-person shooter computer game

An open-source content package for Quake III Arena licensed under the GPL, effectively creating a free stand-alone game. You do not need Quake III Arena to play this game.

free the multiplayer version of Postal 2: Share the Pain, the multiplayer expansion to their controversial FPS Postal 2. Share The Pain contains 14 multiplayer maps, 25 playable characters, 11 crazy weapons and 4 different gametypes.

A GPL first-person shooter by Alientrap Software. with nine weapons, 24 official maps and over 240 community created maps, as well as 15 player models.

America's Army is a video game owned by the United States Government and offers accurate FPS action

Tribes 2 (commonly abbreviated to T2) is a sci-fi first-person shooter (FPS) computer game based in the fictional Earthsiege universe

Set in 2040, gamers participate in the conflicts of tomorrow in urban and open field infantry combat.

An online FPS based in the Wolfenstien universe with two teams Axis and Allies.