S.T.A.L.K.E.R.: Clear Sky VS Unreal Tournament

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.

Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.

Shadow Warrior - Shadow Warrior by the famously known Flying Wild Hog is a mix-up of brilliant Action, First person Shooter and combat elements and offers a thrilling game-play and story to enjoy.

Quake - Quake is a series of first-person shooter video games released by id Software.

Rise of the Triad - Rise of the Triad is an Action-Adventure, Role-playing, FPS (First-person Shooter), Open World, Female Protagonist, Science-fiction, Single and Multiplayer video game created by Interceptor Entertainment and Apogee Software.

Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.