I already have Wipeout HD along with Killzone: Liberation (I think that's the one I have, anyway). So that narrows my choices slightly. I'm thinking I'll get Dead Nation as it has offline co-op which is great for Danielle and myself. Any suggestions on the other choices from you lot? *does a bit more research*

EDIT: It's between Ratchet and Clank: Quest for Booty and Little Big Planet for my second PS3 choice, and I have no idea which two of Little Big Planet PSP, ModNation PSP and Pursuit Force I'll go for. :S

EDIT: Gonna go for LittleBigPlanet & Dead Nation for PS3, both have offline co-op and that works well for me and Danielle. And uhm. I assume this is per PS3, not per account.