Remember the Soap Box Derby? Maybe when you were a kid you wanted to be in it. While some of the early vehicles at what's now known as the All-American Soap Box Derby may have been made out of actual soapboxes all that truly mattered was that they were gravity propelled and used standardized wheels. Otherwise, participants could build any kind of engineless car they wanted and race it downhill for prizes.
OK, so the soapbox derby isn't really unusual enough for this list. But the Red Bull Soapbox Race, which emphasizes not just velocity but outside-the-box (and off-the-wall) creativity, really is. "Cars" from past races have been in the shape of a piano, a giant cob of corn and -- you're forgiven if you're having trouble imagining this one -- the Golden Gate Bridge. Technically, of course, this isn't an auto race because the vehicles aren't self-propelled. But when the race is this entertaining, does anyone care?