The Honda Motocompo is very collectible in most parts of the world for those in the collector circles. It's actually a handy bike that can go 35 mph, fit in your trunk or hatch. It's perfect for airplanes, boats, etc.
Honda hasn't made that bike for awhile now, but parts are still easy to find in Japan.
I'd take a dream 50, Monkey R or Monkey first, but that bike wouldn't be bad to own...