in a restaurant bathroom: a three ringed bulls-eye in permanent marker drawn on a wall opposite the toilet with about 1000 dried snots stuck mostly in the 1st ring.
on a wall at a urinal "look down, the joke is in your hand"
On the back of the door of the science library toilets at university:"I have a 10 inch noodle""Is that in binary?"laughed for ages at that one!