2010 Ferrari 458 Italia
I fucking love this car. I've got it up to an R3 and it is the most balanced car I have. It is amazingly fast, has great acceleration, and I can really make any turn especially with traction and stability control off (without them I can really wipe the car's ass around corners).
I used to really like AWD in Forza 3. But, with 4 and with the driving assists off this game really allows for well done controlled drifts. I find trying to drift around corners in AWD cars next to impossible. But, with 2WD, I can really carry a lot of speed around corners.