Halo 2, the ultimate multiplayer experience. Too bad I don't have X-Box Live!
In Halo 2 you will play as Master Chief of course, but then you will switch and play as an outcast Elite, who for some reason everyone calls the "Arbitor". At the outset of the game to get some respect back from his peers I suppose, the Arbitor's job is to find someone leading a revolt among the Elites called the heretic, and kill him. Of course things get more complicated after you accomplish that mission. As Master Chief your job throughout the game is mainly to kick behind and don't bother with any names. As the story progresses it become more and more confusing, until at one point Master Chief and the Arbitor are being given a lesson in plot advancement from what looks like the man eating plant in "Little Shop of Horrors". (Believe me, I wish I was kidding) However, plot confusion and nonsence will not prevent you from enjoying the many excellent confrontations you will be experiencing in this game, although the game in general would have benefited from a few more boss battles, I believe. The final boss battle is a bit of a letdown considering the fact all you do is fight a Brute carrying a big hammer. I guess he usually uses the hammer for tenderizing his hamburger.
So, get of multiplayer and enjoy (and be baffled) by the single player version of Halo 2!