Wadsworth

 is your personal Mr. Handy butler in Megaton, which you get, together with a house, for disarming the nuclear bomb that lies in the middle of the town. He can give you instructions on how to spruce up your house, give you haircuts and tell you jokes. Wadsworth can also give you purified waters, but only up to five at a time before needing to recreate his supply.

Appearances
 appears only in Fallout 3.