Monowheels have certainly not have taken off in any big way, but just like ekranoplans you sort of wish they had. This French model from 1932 even has very clever steering. Watch the inventor do le burnout!
The clip is from a period Hungarian newsreel and this is what the title card reads:
Inventor shows off miracle machine on streets of Paris.
I wonder if a small block would fit in there.
Hat tip to markoferko