Ten-foot Pole

The ten-foot pole is the most useful item an adventurer can have. Part of this is because it has great practical value. You can use it to make sure you're out of weapon reach, attach a weight at the end to set off traps, use it as a walking stick during those long dungeon crawls, or whack a particularly stupid party member of the head with it. A ten-foot pole also has great psychological value. If a non-adventurer sees an adventurer with a ten-foot pole, the adventurer can then borrow any number of items that were conveniently lost or forgotten such as rope, backpacks, potions of waterbreathing because the non-adventurer assumes that the adventurer would normally carry these on him.