DotA 2 - Dota 2 is a Free-to-play, Action-Adventure, Multiplayer Online Battle Arena, Single and Multiplayer video game created and published by Valve Corporation.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Payday: The Heist - Payday: The Heist is an Action-Adventure, Co-op, Heist, Tactical, Online, Team-based and Single-player video game developed by Overkill Software and published by Sony Online Entertainment.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Tom Clancy’s Rainbow Six Siege - Tom Clancy’s Rainbow Six Siege is an FPS (First-person Shooter) with Tactical elements developed by Ubisoft Montreal and published by Ubisoft.
Quake - Quake is a series of first-person shooter video games released by id Software.