Don't be lazy and say everything - I want specifics. Here is some of my list:
Mini Cooper Coupe:
With the turbo motor out of the S, I think a RWD version would be very entertaining
Acura Integra Type-R:
It's a cool car as is, but RWD would have made it a lot better.
Dodge SRT4:
Light weight, RWD, and easily modded turbo engine would have been a lot of win.
MazdaSpeed3:
Same as above, but this would actually be great with an AWD system as well.