A bone stock 1993 Mazda RX-7 R1. Debatedly the purest 'affordable' sports car ever made. That is the sensible choice and I almost nabbed one last year....
If money was no object. Without a doubt, a Porsche 993 Turbo. These things are going for insane money now. Just an unreal sexy car, and so frikking scary and twitchy to drive. It's fast, but it tests the driver. And that's part of the fun.
