Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Insurgency - Take to the streets for intense close quarters combat, where a team's survival depends upon securing crucial strongholds and destroying enemy supply in this multiplayer and cooperative Source Engine based experience.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Hawken - Hawken is an Action, Free-to-play, FPS, Robots, Science-fiction, Tactical, Futuristic, MMO, Co-Op and Multiplayer video game created and published by Reloaded Games.
Quake - Quake is a series of first-person shooter video games released by id Software.
Deus Ex: Invisible War - Deus Ex: Invisible War is an Action-Adventure, Role-playing, FPS (First-person Shooter), Science-Fiction, Stealth, Dystopian, Female Protagonist, and Single-player video game developed by Ion Storm and published by Square Enix.