Best rush in a proper car so far? I'd have to say having a ride with my uncle in another uncle's Alfa 146 when we went back to Malaysia for our Chinese New Year family reunion a couple of years ago.
He knows I like cars, and he himself is a minor petrolhead, but even then I was completely taken by surprise when he just called over to me while I was standing outside the house looking at the car, and really casually said, "Come on, let's go for a spin".
Well when he said "spin", I had no idea he actually took it literally! We didn't actually spin or crash, but that was the craziest drive I had ever been on a public road... Shifting at 5500-6000 rpm, shooting past Protons and Peroduas at 150kmh (almost 100mph), on a single carriageway no less! Was definitely very scary and as a result of that, a huge adrenalin rush.
If I could do that all over again, I definitely would, scary as it was. To this day, my mum doesn't know what exactly he got up to on that day, but suffice to say she'd rain hell on her brother for driving so recklessly :D And it wasn't even his car...