Actually I'm lying, I played Time Splitters 2 in split-screen multiplayer mode all the way through the main storyline with my brother and it was awesome. But 99% of my gaming is done on P.C. and playing multiplayer games online against people who spend every spare minute of their life perfecting their skills in that particular game holds little or no appeal to me.
Oh also, multiplayer mode in San Andreas. Man, did that suck!
EDIT: Actually I'm going to tell you all about the multiplayer mode in Ico, because you probably haven't played it and it was hilariously bad. It was one of the things you unlocked as a reward for finishing the game. If you've played Ico, you'll know that there are two characters: Ico, and Princess Whatsername. Princess Whatsername has only two functions: look winsome, and open doors. She's pretty good at both. The rest of the time she spends being threatened by black inky ghosts, and compulsively running towards Ico whenever he calls her.
In the multiplayer mode, the second player plays as Princess Whatsername.
If person playing as Ico presses the "call Princess" button, the Princess will go running towards him. The person playing as the Princess has no control over this.
If you've played Shadow of the Colossus, it's like unlocking a multiplayer mode, and the second player gets to play as the horse.