M3

(then again, i have one...)

For a brief moment I was tempted to answer in McLaren, Ferrari, Porsche style, but I actually don't really want one of those. For me, a car must carry at least four people and have decent amount of trunk space before it can even be considered. I drove a 911 Turbo for a week one time, and it turned out to be rather inconvenient.

This is of course, working from the standpoint of limiting this discussion to what your "primary" day-to-day car would be.

John