Alien Swarm 

Alien Swarm is a co-op squad-based shooter UT3 mod. Set in the distant future, the players take the role of a Commander in the Interstellar Armed Forces. They must guide their squad of marines through Swarm infested colonies, overrun bases and outposts, to achieve a variety of objectives.

Featuring Assault Rifles, Heat Tracking Guns, Sentry Guns, Flamethrowers and more. Alien Swarm can be played single-player or online co-operative multiplayer, with a strong emphasis on teamwork between the marines in both forms of play.

Alien Swarm is now on Steam, as a Source Mod.

guy: wanna play alien swarm??
guy2: the Steam version or UT version?
guy: what Steam version??
guy2: it just came out on Steam as a Source Mod
guy: well, like all urban dictionary definitions, i have to say something perverted now so-
guy2: ASS CLOWN!
guy: hey! i was gonna say that!
guy2: TITS!

Alien Swarm by Hoffer July 18, 2010

Alien Swarm Rage 

Noun - A type of severe anger that is specificly brought about by stupid noobs who can't play Alien Swarm right who often die or TK, bring the wrong equipment, make major tactical errors, or just get lost all the time.

Person 1: "Those flame thrower toting idiots with us couldn't flame their way out of a paper bag!"
Person 2: "Let the Swarm Rage go man, they're new to the game!"

Alien Swarm Rage by Anosola August 30, 2005