Ekranoplan Casspian The Russian Tank-Ship-Plane. Not exactly a plane but still cool. It flies just over the water because of ground effect. So it can haul a heavy load very efficiently compared to getting it up to altitude. Or floating.
The German Focke-Wulf Huckebein was a jet-powered fighter aircraft designed as the successor to the Messerschmitt and other day fighters in Luftwaffe service during World War II. Only a few proto-types were developed.