Captain K Mart - doesnt afraid of anything
Honorable Mention (I guess): Halo 3
It's not as much of the game itself, but the fact that it was really one of the last multiplayer juggernauts that was release before the party system was introduced to Live, which screwed up a lot of the community.
Like, I have about 90 friends on Live, about 50 from real life, about 30 from Halo 3, and about 10 from a bunch of other games.