Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Assassin’s Creed - Assassin’s Creed is a best long running and extremely popular series of open world video games which mixture of action, adventure and more importantly stealth into a single experience.
Quake - Quake is a series of first-person shooter video games released by id Software.
The Saboteur - The Saboteur mixes in the regular setting that many open world action adventures travel to simply by using a World War II theme instead.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Prototype 2 - Prototype 2 provides a combination of open world gameplay and also action adventure using a fun (and powerful) turn.