Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux. Xonotic is a direct successor of the Nexuiz Project. The project is geared towards providing addictive arena shooter gameplay which is all spawned and driven by the community itself. Xonotic is a direct successor of the Nexuiz project with years of development between them, and it aims to become the best possible open-source FPS (first-person-shooter) of its kind. New trailer coming soon Please post all support issues in the forums for the game.
One of the best Arena FPS I've ever tried! Different from the others, really funny and competitive.