It's a HL2 MOD, really fun, and well planned. You have 3 (4?) classes of armor to pick from, then 4 weapon types based on the class of armor, and then various implants that help you, hinder the enemy, or heal nearby teammates. Then you spawn and try to take various objectives.
If you play, or start playing, tell me! I play and I am on a decent server; no swearing or trash-talking. (WHen I die 5 times to 1 kill and NO ONE makes fun of that, you know they are decent players)