It's a free FPS on the quake 3 engine. Obviously, this means the graphics are nothing to call home about, but they really aren't half bad, either. It falls somewere between Counterstrike, Call of Duty, and... well, Quake, in terms of gameplay. Sprinting is very quick, wall jumps are possible (to an extent), and the game moves *very* quickly. Action is almost constant, which is good. The realism I was comparing to CSS or CoD comes in the guns: you will go down quickly. Weapons are lethal and accurate (unless you fire continuously, in which case they become useless). There's no regenerating health: you can bandage yourself to stop bleeding, but injuries take away from your stamina (which does recharge, and is needed for sprinting and jumping). It's got the normal collection of modes, CTF, Team Deathmatch, FFA, and a CSS-type bomb mode, and a very active mapping community. Overall, it's quite a bit of fun to play, and I've been doing a lot of it lately .
EDIT: forgot to say, it's available (and works well) on PC, Mac, and Linux. And all can play with each other.
Edited by Jok3r, 06 June 2010 - 01:40.