Difficult to beat the winged todger and knackers that appeared all over RAF Gutersloh c. 1968 when a visiting French fighter squadron departed. They were spray-painted on stencils. The SWO man went berserk of course, and he had them disappeared before the last fighter was in the air.
BUT the one on the Met Office [ground floor of the tower] survived because it was on a window shutter. I was on morning shift, had the shutter whipped off and had it hidden.
A good few years later when I was the inspecting officer it still survived.
I wonder.