Waterman Arrowbile
The Waterman Arrowbile landed on this list because of its road capabilities, as it’s the first of its kind. You could fly the plane-car hybrid around in the air and also drive on the roads. All you needed to do was detach the wings. Studebaker executives ordered five, anticipating heavy demand. In the end, though, there was much less demand than the company thought such a novelty would produce. Only five of these were ever built. It was a nice idea, but proof that not every concept is worth making for the market.