the other day I saw a Subaru Brat that was in mint condition, compleat with the rear facing bucket seats, it was tiny! 4 wheel drive, and looked like it would be awsome to drive! altho they apparently only get 30mpg at best, I would think you could do an engine swap to fuel injection and improve that.
I have a '83 civic that I'm waiting for the weather to get warmer, I realized the other day that it's about the same size and shape as out Geo Metro.
I would say that a N600 would top my list of a cute fuel efficent collectable vehicle.
I know it's not as classy looking, but a King Midget would be awsome as well, powered by a 10HP Wisconsin engine and a two speed automatic belt drive.
another one is the HMV FreeWay, 80mpg three wheeler, came in gas or a diesel option, I passed one up a few years back for around $1,000.
Tomarrow we are going to look at a
ComutaCar, 1980 two seater, 50mph top speed, 40mile range electric car (4 wheels).
I personaly think that having fuel efficent vehicles that stand out is a good thing, put a little tag on it, and take it to car shows, get people who are in to cars wanting more then just speed.