I think the rarest bike I ever owned was the 100cc 1971 Rockford TAKA.
These were built with Bridgestone tooling in the early 1970s. I never saw any more, other than the ones my father and uncle sold from their motorcycle shop in Atlanta, Illinois.
The next rarest was the 500cc Ossa Yankee-Z
. If my memory is correct, Yankee Motors from Schenectady
New York, built less than 800 units, of which my father sold 11 of them.
I had the most fun with a 1973 Ossa Pioneer
One of the very few street bikes I have owned was the last year production of the 2-stroke water cooled 3 cylinder Suzuki GT750