Comment by TheOtherHobbes

I'll vote for the Lippisch Aerodyne. Picture here:

http://i.kinja-img.com/gawker-media/image/upload/s--BN7-YDzh...

Arguably an update of the Stipa-Caproni from the 1930s:

https://en.wikipedia.org/wiki/Stipa-Caproni