Lyndon Johnson's Amphicar. Produced from 1961 to 1968, the German-built Amphicar could also double as a boat. Johnson was quite the comedian and made a pastime of giving unsuspecting visitors rides in the oddly shaped convertible at his Stonewall, Texas, ranch.
The Amphicar is the world's most common amphibious automobile, a machine that works as well in the water as it does on land. Amuse your friends. Scare the local fish. Whatever. But most of all, drive an Amphicar just once, so you can understand why no one ever needs a car that doubles as a boat. Roads are dry for a reason. Also, former President Lyndon Johnson drove one. Enough said.