I want:
Wheels
Engine
Comfortable seats
Windshield
Windshield wipers
Heating and A/C
Place to put things in it
I'm not very picky, but numbers 3 and 7 are usually where I find the most problems with cars.
I do have to admit though, I get a lot more picky when I'm playing Grand Theft Auto. If street laws weren't at all enforced, and the worst thing that could happen if I got into a car accident was I respawned at a hospital 6 hours later, I might be a lot more interested in vehicles. But as it stands, I take the much more practical stance on owning a vehicle.
If this topic was simply what kind of car you'd like to drive for an hour or so one day for fun on an empty road with no cops, it'd have to be the
Ariel Atom though.