To preface, the guy who lives next to my aunt and uncle, just up the street from me, is a VP for Hasbro. Yes, THAT Hasbro. SO they get company cars. Their current one is a slightly used 745 (and not the Banger'ed one). Before that, though, they had a 545, which I rode in on one occasion. I believe it was a 2001/2002-ish.
The nicest car I ever drove goes to a 2000-04 (not sure of the year) Land Rover Discovery (II?). That was a pain. I had to move it from the side of the (very busy) street, down the road a bit and move it onto the sidewalk. The reason being, an elderly gentleman was walking down the sidewalk, and missed the curb. My parents stopped, and while my father and some others were helping him out, I offered to move some of the cars they were in. This particular one belonged to a nurse. She also happened to be almost a foot shorter than me, so I barely squeezed into the drivers seat, with my knees hitting the lower dashboard. I couldn't find the seat controls, so I started to attempt to put the key in the ignition. After some trouble, I finally looked at the key, and saw the Corvette logo on it.

I finally get the right key in, and the car started and finally move it. Of course, as I get out, I find the seat controls...
An honorable mention has to go to a Mercedes kit car I got to drive once. It was a body kit to make the car it used to be (an Escort) look like an old school MB convertible/sportscar, chromed exhaust tubes on the engine bay and everything. I'd say its overall size was about the same as a Morgan 4, perhaps sitting a little lower, like a Caterham. Of course, despite the eight pipes, it only had four cylinders, and thus needed about 1/4 throttle to move from a stop, even with an automatic!
Nicest car I've ever sat in was some type of Ferrari from the 1980's, not sure what kind though. It was in the car museum/collection at the Yankee Candle main store in South Deerfield MA. It was wired to make engine noises when you stepped on the gas.
