It isn't widely known, but Shelby American had a brief relationship with a network of Latin American dealers and businessmen who organized a line of Fords with Shelby-endorsed modifications and cladding from the late 1960s to the early '70s.  The most notable was the Mustang.  Instead of just prettying up a notchback a la the California and High Country specials, Shelby de Mexico offered a little bit more with unique hooding and a faux fastback roofline--a cosmetic feature I adore.  The roofline was altered by fiberglass extensions, covered by vinyl roofing.  Only about a tenth of the originals have been found.

Which forgotten classic muscle machine, pony car, or sleeper ranks No. 1 on your list and why?