Oh yeah, Rover SD1 without a doubt.
As a nipper, out walking the dog one evening one flew by my parents house on the A57 at what my dad estimated as "...over the ton...". I had never seen anything going that fast, so close. A lasting impression. [For context, my dad also reckoned that the frequent two-tones we used to hear at five-to-nine of an evening were coppers trying to get to the local chippy before it closed.]
That being said, before the SD1 came along, it had to be the 2500Pi Triumph. A straight six with Michelotti styling, what's not to like?