Since I was a wee lad, I always lusted after the Lamborghini Countach. I got a Matchbox car of one and for years I couldn't even say the car's name. It was orange, and by today's standards, quite ugly. But damn, I was in love with that car, and I was certain it was the fastest thing on four wheels.
The irony of it is, the stock SRT-6 is faster than a 70's Countach. LOL
Another obsession car for me was the Porsche 959. I have this intense desire to smoke all four tires at once.
Then there's the modern-not-so-modern dream car for me: the Morgan Aero Supersports. As John said above: it is something "different".
http://www.youtube.com/watch?v=2MxhG1-QAfw