Wolf Team - Wolf Team is the excellent game for those players who love playing FPS games.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Combat Arms: Reloaded - Combat Arms: Reloaded is an Amazing, Tactical, Free-to-play, Online, Co-op, First-person Shooter (FPS), Military-themed, Open World, and Multiplayer video game developed by Nexon and published by Lithtech Jupiter.
Quake - Quake is a series of first-person shooter video games released by id Software.
War Rock - War Rock is a Superb, Action-Adventure, First-person Shooter (FPS), Online, Military-themed, Open World, Tactical, and Multiplayer video game developed and published by Dream Execution.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.