The way I see it, in a perfect world a person would have four cars -- a commuter (in an area where mass-transit infrastructure is woefully undeveloped, at least), a comfortable and classy Sedan, a purist sportscar, and a beater for carrying stuff or towing. Here's what I'd want for each:

Commuter:
An efficient but classy high-tech modern commuter car, something the US government won't let me have. I'd take one of the following: M-B A190 lwb, Audi A2, Citroen C3 Pluriel. The BMW Mini is close, but not nearly as much space or practicality as the above three.

Sedan:
My current 1968.5 Citroen DS-21 modified with a lightweight engine that's considerably more powerful, refined, and efficient than the iron-block pushrod 4 Citroen shipped it with, such as the M-B 3.2L twinspark V6, Subaru H4, VW VR6, or a non-turbo Mazda rotary, as well as new hubs to support modern wheels and tires. A tiptronic-style automatic or CVT transaxle would also be glorious. Oh, and the development of the brilliant hydropneumatic suspension used on the mid-1990s Xantia Activa. But one mustn't get greedy.

Sportscar
A Lotus Elise. Since, the government doesn't want me to have one, though, a Panoz AIV (made here in Georgia using some of the highest technology in the industry) is the next best thing, but I'd REALLY want the lithe little Lotus!

I prefer the idea of a lightweight, fuel-efficient, ecologically sensitive useless car to a heavy, huge-engined, gas-guzzling one.

Practicalmobile
In a perfect world, I'd combine this one with my commuter, and drive a Citroen C3 Pluriel. (The Pluriel can be a sedan, spider, or pick-up.) However, if I had a boat or something I'd be looking at a W124 TE, perhaps massaged with a 400E's driveline...