Can anyone think of some good split screen co-op games on the 360 and the PS3

[Azure9]

An old time friend came over to my house today and oddly we couldn't think any good split screen co-op games to play besides halo games and resistance. Can anyone suggest to me some good games.
I'm not looking for games that are co-op that share the same screen such as castle crashers.

 

[RJ 17]

The Left 4 Dead games if you're into mindless Zombie slaughter.

 

[Sniper Team 4]

Gears of War and Gears of War 3--Be warned: Gears of War 2 has a glitch that will corrupt your progress if you play it split screen. And no, this glitch still hasn't been fixed. It do not happen to everyone, but it happened to me. Very annoying. Had to reboot my entire profile on that game.

Left of Dead Series, Resident Evil 5 (hey, I like it), Portal 2, and Call of Duty World at War. Those are all I can think of. The Modern Warfare games have Spec Ops co op, and you already listed the Resistance and Halo series.