A DMC would be awesome. But I would love to have the first, "crappy camera" bumblebee from the first transformers movie... Thought that car was pretty sick in all its crappiness.
I have a love of seriously old and incredibly slow cars, and I'd absolutely love to do the 'Old Crocks' London to Brighton Veteran Car Run which is open to pre-1905 cars, and is run every year on the first Sunday in November. So my movie car of choice would have to be Genevieve from the 1953 classic British movie of the same name. It's a 1904 Darracq.