Call of Duty - Call of Duty is a first-person and third-person shooter series by Infinity Ward.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Quake - Quake is a series of first-person shooter video games released by id Software.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Unity - The multiplatform game creation tools for everyone.