Cooperative Shooter Games

Hi -

I am looking for a "shooter" game (Call of Duty, Assassins Creed,...) that I can play with my 10 year old son together, meaning as a team, on the PS3. In other words, we want to be on the same team and complete missions or fight together, not against one another or separately (and not from two different PS3s).

We have COD Modern Warfare for the PS3 but it does not seem to have this feature (I thought multi-player feature meant cooperative play but it does not - it's player vs player).

Thanks for your help.

Borderlands is a good game for co-op. It actually has split-screen which is a rarity anymore. And most Call of Duty's should have some sort of couch co-op. I remember being able to play online with another person but I don't know if the most recent ones still have that.