For me it has to be the Lambo Countach LP 500, because it was the first super car (by the standards of its time) that I ever got to drive on the open road. This happened many, many years ago when I was still an ignorant apprentice, but now that I think back on it, I am wondering why the uncomfortable seating position, poor visibility out of it, the very heavy clutch and mushy gear shift did not put me off super cars in general, and Lambos in particular, for life back then.
Nonetheless, even though I have lost my enthusiasm for cars long ago, I must admit that my first experience with a super car was my coolest experience with super cars, ever.