Two of the biggest mysteries I've ever encountered are:
* When you're in the fairway of a golf course, 50-150 yards from the green, with the ball below your feet (fairway sloping away from you) and the green you're aiming at sloping in the opposite direction, where exactly do you aim the ball? (Assuming the hole is in the middle of the green)
* Is it possible to construct a device that would bowl a perfect 300 game every time? If so, what would it look like?