Reddit recently featured a discussion on the best videos lasting 10 seconds or less, and most of the videos mentioned were funny in some way or another.
Someone has compiled all of the videos featured in the thread into a compilation lasting a smidgen over seven minutes. The challenge is therefore to watch for as long as possible without succumbing to laughter.
I lasted all the way until the orangutan stole the banana, but the clips beforehand had softened me up somewhat so that I was more liable to crack.
I doubt anyone could sit through the whole thing without laughing at least once. Mainly because the clips cover every different type of humor there is, so something is bound to tickle your funny bone.