A good pair would be the British Bristol 188 (above) and the American Douglas X-3 Stiletto (below).
Both experimental aircraft from the golden age of probing the supersonic possibilities, both essentially failures - to be fair, both more to do with inadequate engines than airframe issues, but it has to be said their concepts were ultimately found to be unviable. Another connection is that both featured exotic metals in their primary construction. Stainless steel in the Bristol and Titanium in the Douglas, and both providing major headaches for their manufacture.
What other beautiful failures can you think of?