Up.

This is a post dedicated to the wonderfulness of Up. Up is a direction, a very nice one, too. Birds use it frequently, as do Blimps, Planes, Balloons, Catapults, Bats, and Submarines. It is two letters, and scores 4 points in Scrabble. Down is the opposite, as well as Pu. Your spirits can rise (going up) when you here something really good has come up (there it is again). In these ways and many more, the usefulness of the word Up continues to rise.