If you can get it cheap I highly recomend that you get GunGrave. A very fun arcade feeling game where you just blast the shit out of stuff. The game does not fool around either. Story happens between levels and the gameplay is (although I have heard many complaints) rock solid. The levels even start by saing "Kick their asses!" or something like that. I can say I would have spent much more than I did (I only paid $5) but it is very short and not a whole lot of replay. One of the most stylish games next to ICO.
Also if you get SH2 for the PS2 make sure you get the Greatest Hits Edition (it has all the Xbox extras).
Also Mobile Light Force 2 is a good $10 purchase, but yes it is a butchered game. The gameplay is still 100% there and it is like renting, if you like it, buy it from JP (or just get the sequal).
I don't really like RPG, but the rest of these recomendations look solid.