I honestly don't have much atm
Uncharted 2.
Uncharted 3.
Killzone 2.
Medal of Honor.
The co-op missions for Uncharted 2 & 3 would be the interesting stuff imo.
But mp would be ok if that's all you have, or if you don't want to try the co-op stuff until you've played the single player stories yourself.
I grabbed some free map packs for 3 last night, but I'm not sure if they're free for you too or if I got them because I had the physical version and a working network pass
The other 2 games I listed I'm not really keen on playing, but if you have them and want to try that's fine.
I know the Uncharted games work fine with mp or co-op anyway.
I haven't got it installed yet, but I'll download Borderlands 2 at some stage...so maybe that is something else you may want to try.