Ithacus was a 1966 study by Douglas, producers of the DC- series transport aircraft and the Thor IRBM, for a sub-orbital troop transport.
The D-21 was a supersonic reconnaissance drone used briefly in the 1960s and 1970s.
HMAS Melbourne was the Royal Australian Navy's last aircraft carrier (to date).
The Saunders-Roe SR.45 Princess was the largest all-metal flying-boat ever built. Only three were made, and none was ever sold.
The XV-4 was a prototype V/STOL aircraft built for the US Army.
Yeah, I pretty much have to do this one, don't I? The Valkyrie was to be a Mach 3 high-altitude nuclear bomber.
The Vigilante was a carrier-borne supersonic bomber.
The TSR-2 was to be a highly capable low-and-fast bomber and reconnaissance aircraft. It was famously cancelled in 1965.
The Hustler was not just the first aircraft to be named after a pornographic magazine (this is a lie, it first flew nearly twenty years before that was thought of), it was the world's first operational supersonic bomber.