Arma - Experience true combat gameplay in a massive military sandbox.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Rust Game - Rust’s world is harsh. The environment is not kind. Bears and wolves will chase and kill you. Falling from a height will kill you. Being exposed to radiation for an extended period will kill you. Starving will kill you. Being cold will kill you.
Quake - Quake is a series of first-person shooter video games released by id Software.
Infestation: The New Z - Infestation: The New Z is a Free to play, Massively Multiplayer Online Role-playing, Third-person Shooter Horror, Survival, and Open-World video game developed by Fredaikis AB and published by OP Production LLC.
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.