Those DAYUM PSN games.

[legendary_mantis]

The demo for Eat Them! Gives the game 0 justice. It's very fun with a variety of levels and moderately in depth monster design. (stats and stuff)

Castle Crashers is also a fun game, but best played with friends.
Assuming you haven't played it, or don't own it on xbox, it's a action rpg and it's a rather silly game.

If you get/have a playstation move, get House of the dead 3 and 4, resident evil dark side chronicles, umbrella chronicles and dead space extraction.

For full PS3 game downloads, I reccomend MAG. I don't know why people give it flack as it's a solid game. Every thing moves smoothly, it's quiet balanced actually, and the skill tree system is very well done.

If you're looking for some Contra, Hard Corps: Uprising. It's a bit more RPG-ish though. You get exp/money and spend it on skills. It gives you the option to turn them off though.