Unfortunately, Mattel only produced this Hot Wheels car as a prototype and never actually released it to the public. So, only ten of them exist in the world today. But, it does have a pretty interesting back-story. It was inspired by the Red Baron World War I plane and featured a German helmet in place of a roof, a pair of machine guns, and a white plastic interior. Had it hit stores, it would be much, much higher on this list than it is today.