Mitsubishi Evo IX, Works Modified.
Fast, handles well, tail likes to hang out to a controllable degree.
However, I recently purchased the Audi TT thinking that It could be a serious track day car. Then I found you can drop the R8 V8 into the machine and this puppy makes Vipers look like they are standing still!
I second the Evo. I own less than 10 cars because I haven't really started collecting. I spend more time competing with autolog. But the Evo is the best handling and quickest car I have thus far. I can handle it better than my R34 that I thought was great until I Works converted the Evo.