"Prinny: Can I Really Be the Hero?" and its sequel "Prinny 2: Dawn of Operation Panties, Dood!" are both incredibly hard and frustrating 2D Platformers on the PSP. Prinny 2 is a billion times more cheap, and actually pretty badly designed compared to the original though, so if you do want to try one of them, go with Prinny 1. Of course if you're looking for hardcore dungeon crawling RPGs, you can't go too wrong with the "Etrian Odyssey" games.