I wan to introduce Sauerbraten, a game that is fun and can be run on low end systems! It is kind of like Quake and Unreal Tournament, but it is really fast paced and action based. There is also large fan base that plays the game, so there is always somebody to fight against. There is also a level editor, so one can make his or her own maps and play on that.

The official webpage is here: http://sauerbraten.org/

As I said before, this runs on really low end systems. This was made in 2004 (don't get scared, graphics are still really good) I get 144 fps on my intel core i3 third generation and my Intel HD 4000.