Douglas X-3 Stiletto

Good name. Only one Douglas X-3 was ever built. 
As part of the American supersonic program, it was the first conventionally launching and landing plane capable of Mach 2, the previous ones were launched from a "mother ship". 
Engine development problems limited power and the the plane never achieved its potential. After less than 4 years it was donated to the U S Air Force Museum in Dayton Ohio, where it can be seen today.