Wadsworth

 is your personal Mr. Handy butler in Megaton in the year 2277, which you get, together with a house, for disarming the nuclear bomb that lies in the middle of the town.

Effects of player actions
He can give you instructions on how to spruce up your house, give you haircuts and tell science-related jokes (only one at a time, so he can recharge his 'humor emitter array'). Wadsworth can also give you Purified Water, but only five at a time before needing to refresh his supply. It takes 7 days for him to refill his supply.

Quotes

 * When you buy the My First Laboratory and ask Wadsworth to explain what it does, he'll explain that it can be used to remove addictions, and then add under his (figurative) breath (without appearing in the dialogue subtitles) "knowing what you're addicted to it might blow out the program all together."
 * When you approach him, one of his phrases is "How may I serve you Master?" Followed by (not in the dialogue subtitles) "...not that I really want to." (male characters only)
 * If you start a conversation with him during the evening, he says, "What can I do for you?" He will then say (not in the subtitles) "...nothing I hope."
 * In another one of his phrases, after he says "It's good to see you alive and well, sir/madam," he will also say (not in dialogue subtitles), "...good to see you, anyway."
 * If the player has purchased the Med-Tek Infirmary for his/her home, Wadsworth will suggest the player use it whenever he notices the player has been wounded. Without the Infirmary upgrade purchased, Wadsworth's response changes to: "It appears you've been wounded, sir/maam. May I suggest you seek medical attention, as soon as possible?" (with a worried tone).

These are just jokes:
 * I was going to the clairvoyants' meeting, but it was canceled due to unforeseen events.
 * Did you know that the best contraceptive for old people is nudity?
 * It is common knowledge that irradiated cats have 18 half-lives.
 * Two cannibals are eating a clown, one turns to the other and says "does this taste funny to you?"
 * Photons have mass? I didn't even know they were Catholic.
 * I once visited a crematorium that gave discounts to burn victims.
 * Two atoms are sitting in a bar. One says to the other, "I think I've lost an electron." The other asks "Are you sure?" To which the first replies, "I'm positive."
 * A neutron walks into a bar. "How much for a drink?" To which the bartender responds, "For you, no charge."
 * War does not determine who is right - only who is left.

Bugs

 * If the player kills Wadsworth and then reloads a previous save, it is possible that Wadsworth will become a floating corpse of himself.
 * The dialogue contains a rare example of typo in the subtitles:"It appears you've been wounded, sir. May I suggest you utilitze your infirmary."
 * More often than not when the player interacts with Wadsworth in afternoon, it will still say "Good morning sir" regardless of the time.
 * Sometimes Wadsworth will stay in the player's bedroom, or get stuck on the player's bed, preventing the player from entering and using their bed.
 * Sometimes if the player is not aligned with Wadsworth's eyes while getting a haircut, half of players face will be cut off from the screen. Crouching may result in the screen showing the player's pelvic area.
 * Sometimes if you kill Wadsworth, exit your house, and reenter quickly, he will have disappeared.
 * When speaking with him, it is possible the focus-changing animation and his movement may result in the PC occupying the same space as him.
 * He sometimes confuses the PC condition phrases: you may enter your home in full health and he advises you to seek medical attention; conversely, he might say, "It's good to see you alive and well" when you're seriously wounded.

Appearances
appears only in Fallout 3.

Behind the scenes

 * The joke, "War does not determine who is right- only who is left." is a quote from Bertrand Russell.
 * His name could be a reference to Tim Curry's Character "Wadsworth The Butler" in the movie Clue. In the movie "Wadsworth" is a rather cynical butler with a distinctive English accent much like the "Wadsworth" in Fallout 3.