Quake - Quake is a series of first-person shooter video games released by id Software.
X-Plane - The world's most advanced flight simulator just got an upgrade. Download the free demo today for Windows, macOS, & Linux.
Call of Duty - Call of Duty is a first-person and third-person shooter series by Infinity Ward.
FlightGear - The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. It also simulates space flight in Earth's orbit. It's flight dynamics engine (JSBSim) is used in a 2015 NASA benchmark.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Tom Clancy’s H.A.W.X 2 - Tom Clancy’s H.