An epic bug hunt featuring a unique blend of co-op play and squad-level tactics. With your friends, form a squad of four distinct IAF Marine classes. Plan your attack using an unlockable arsenal of weapons with countless loadout configurations against a wide variety of aliens. Blaze your way through an overrun, off-world colony, eradicating the alien infestation in environments ranging from the icy planet's surface, to a subterranean lava-flooded mining facility.
I picked this game up when it first launched to the public and just loved it. Even with the content it had then, the game kept me and a few friends entertained for a good few hours. If I recall correctly, it came with a SDK even back then, so the game should have tons of community created content already.
A few words about the game itself. It's an addictive top-down alien shooter with co-op campains (best with friends, trust me). It has class-based leveling and loads of weapon and item combinations. Valve made a few campaigns for it but I'm sure there should be more made by players (unless the game is dead by now) and that adds a bit replay value.
All in all, I have fond memories of this game and the only probable reason I ever put it down was because most of my friends moved to different games. The game has a lot of potential for entertainment seekers and challenge junkies, but a lot of it falls on the community's shoulders.