Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Amnesia: The Dark Descent - Amnesia: The Dark Descent is an addictive, Horror-Survival, Exploration, Dungeon Crawling, and Single-player video game developed and published by Frictional Games.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Alien: Isolation - Alien: Isolation is a Horror Survival video game developed by Creative Assembly and published by Sega.
Quake - Quake is a series of first-person shooter video games released by id Software.
Left 4 Dead - Left 4 Dead is an Engaging, Action-Adventure, Horror-Survival, FPS (First-person Shooter), Co-op, Single and Multiplayer video game created and published by Valve.