A Carpenter's Best Tool

Many tools come in handy for a carpenter, especially when they accompany some of our more popular sayings, like "When in doubt, hit it with a hammer" or "Measure once. Cut twice." But my favorite saying is "OWW!" The occasional pain reliever can be the most accommodating tool for a carpenter, especially when one's been kneeling on a concrete subfloor all day.
*WARNING* Use pain reliever's sparingly, even over the counter, for obvious reasons, also the more you use them the less they work.