Valkyria Chronicles - If you like SRPGs, then you have to get it. Not only is it beautiful, it has a great story, and innovative gameplay. Also, you should buy now before it becomes impossible to find.
I'd name more, but all the ones I've played are multiplatform between X360 and PS3 so it doesn't really matter.
EDIT: as for deals, I don't know of anywhere other than buying used on Amazon.com If we lived in the UK you could get tons of games for dirt cheap.