Question of the Night: What concept car that didn't reach production might have changed [automotive] history?

I love concept cars. More of them could/should reach production closer to their concept form. There’s a bunch that immediately come to mind when discussing the topic: Jaguar C-X75, Ford GT90 and Bronco concept (and so many other Ford/Mercury concepts), Lincoln Continental Concept (2002), a bunch of caddies, Chrysler…