Firefight is a great team game because working with other players feels voluntary instead of forced.
The best thing about Halo 3: ODST is Firefight. While a lot of gamers wrote it off as a derivative of Gears of War 2’s Horde mode, it deserves credit for being a much more refined design. Team game design can be seen as a kind of miniature economy or scaled down MMO. The basic rules governing an MMO economy like exclusive resources and mutual goals are distilled and simplified into combinations that can be grasped on the fly. Instead of a Healer and Tank exchanging buffs and timing elaborate strategies, the exchange is much less complicated. A sniper covering you while you close in with a short range weapons is a resource being swapped. You keep the sniper from being overwhelmed, the sniper watches your back in exchange. The individual abilities of a class are now the weapons equipped. Firefight captures the essence of this exchange without forcing the player to participate in it if they choose not to.
Firefight would make a really good XBLA download. It consists of eight levels taken from the ODST campaign re-designed into closed arenas. Two levels can also be played at night to mix things up. Enemy troops drop in at various points or doorways at timed intervals. Five waves of enemies per round, three rounds per set, and 200,000 points total to make par on a set. Waves consist of about three groups of five aliens, give or take, and can be anything from Grunts, Heavies, Brutes, or those God awful bug things. Levels are all varied in playstyle. ‘Crater’ is a big arena with two platforms looking down on it. Getting control of a gun turret on your side is the key to keeping the level under control and not getting overwhelmed. For those more interested in vehicles there is ‘Platoon’, which features a Warthog and has Brute troops drop in on Chopper bikes regularly. Other levels feature complex hallways and tunnels that you have to dart around while enemies close in. To keep things interesting you play as an Orbital Defense Shock Trooper, which means no regenerating health. You have a finite supply of ammo and health kits that restock at the end of each round.