Core77

They almost look like Japanese family crests, but in fact these are different types of screw heads. You've probably seen some of these holding bathroom stalls together, as the unusually-shaped slots prevent those wily pranksters from Lambda House from dismantling the loo with a regular Philips-head.

This entire list was painstakingly compiled by Instructables user arcticpenguin, and is available at the link above as a 29-page PDF document.