Mister Sandman

Mister Sandman is a Fallout 3 Perk.

With the Mister Sandman perk, when you are in Sneak mode, the option to silently kill any human or Ghoul while they’re sleeping is given. All Mister Sandman kills earn bonus XP - which amounts to 50 experience points per kill on any difficulty.

Mister Sandman is performed in sneak mode and by choosing "Pickpocket" on an unfortunate sleeping victim. Choosing "Pickpocket" pauses the game and brings up a menu with the options to "Murder" or "Pickpocket". Chose the former to active the perk. When used, short murder animation follows with the player character looking around and slitting the victim's throat, accompanied by a cartoony jingly fanfare.

Possession of a knife or other bladed weapon is not necessary to perform a Mister Sandman kill, even though the kill animation shows the deed performed with a knife.

Sometimes Mister Sandman victims wake up and cry out before they die, thus alerting nearby characters even with 100 Sneak and a Stealth Boy, or high sneak and the Chinese Stealth Armor. This may happens due to the "stealth" flag being removed from the player while the Mister Sandman killing is in process, rendering the player "clearly detectable", even to sleeping characters as they somehow can observe you while you are sneaking. Also, some victims even stand up, move around, and complain before the game decides to kill them, also alerting nearby characters. It appears as though hostile characters will always wake up if this perk is used on them, thus, greatly limiting the usefulness of this perk for karmatically Good characters.

Bugs

 * Prior to patch 1.0.0.15, it was possible to use the perk on children. This would not kill the sleeping child, but the experience would still be gained, allowing for unlimited EXP.
 * Sometimes, victims will speak when you steal nearby items, demeaning you for your theft. There are no consequences for this, though.
 * The player character will sometimes simply levitate over the victim, with no knife animation playing. The cause of this is unknown, but it seems to always happen after the new patch, even without the Chinese Stealth Armor