I hate seeing this thread go dormant. I know that pretty much everyone already knows what the Porsche 911 GT3 RSR sounds like, but I just want to draw attention to one particular point in this video, 7:14, where it drives by the camera evidently just before shifting up. That sound it truly awesome, and that's a word that I don't use often.
The Datsun that Leonidae posted above has similar appeal to me (and there are plenty of other examples of the same thing). I'm not sure quite what the word is to describe it, but the two sounds definitely share something in common that brings me some sort of visceral pleasure.