Armored Core Series.

Don't know if you are into these games, but I've just gotten hooked on it. Armored Core 2 and Armored Core 2: Another Age are definitely worth getting in my opinion. They are comparable to a Gran Turismo Series only difference is that instead of driving cars, you pilot your custom made Mech(Robot). You can tune your Mech and make all sorts of changes which make it interesting. Oh! Did I forget the amount of carnage you can create. If you get a chance, get a copy or rent it, you'll get into it just as easy as I did.