There are about 3 or 4 variations of Action Quake 2 out there all for free, you just have to search around for it. Action Quake 2 was developed by the A-Team, one member being Gooseman, who went on to do stuff for Counterstrike, the rest going on to do Action Half Life. Fans made Reaction Quake 3, which I don't think ever had a freeware release. Most of the members I use to talk to of that team are never on either, but it was a great team to work for. Unfortunately AQ2 and RQ3 never really get any recognition for being over shadowed by CS, but those mods were ground breaking, and the only real thing before them was Navy Seals Q1, which was horrible.