A visual representation for the notation of a function and its inverse.
Doesn't work as well if you have the stapler on the outside and the staple remover on the inside. Would've been more useful if instead of x, there were a stack of papers. Maybe if I can find some time or if someone has the time...(via MathFail)
PS: If you like this, also check out f(a bag of skittles) over at Sweeney Math.
PPS: Quick google search yields this thread over at reddit. Following comment is by trebor89.
The function f(y) = (staple remover (stapler (y)) is NOT the inverse; it's actually the function commonly known as Gödel's Umlautifier. Simply try it on some trivial input: f(a) = ä.