Xonotic is an FPS game released under the GPLv3+ license.
In this video I show you a complete unedited online CTF (Capture The Flag) match on this server which uses vehicles and other mods.
You don’t need an expensive GPU to run this: even an older integrated GPU will work fine. I was able, in-fact, to play and record the video on the same machine using an integrated Intel graphics GPU.
Hve fun :)