Mister Sandman/Fallout 3

Mister Sandman is a perk in Fallout 3.

Effects
With the Mister Sandman perk, when the player is in Sneak mode, they have the option to silently kill any human or ghoul while they're sleeping. 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". Choosing the former to activates the perk. When used, a short murder animation follows with the player character looking around and slitting the victim's throat, accompanied by a cartoony jingly fanfare.

No karma will be lost or gained from Mister Sandman kills (the player will lose karma for killing a person while detected). In both games, it was possible to harvest unlimited experience by repeatedly assassinating children. Because children are scripted to be unkillable, they will remain alive even after performing a Mister Sandman kill, allowing for more Mister Sandman kills to be performed. This was fixed in patch 1.0.0.15 in Fallout 3.

If the player has the Contract Killer or Lawbringer perks, killing non-player characters with this perk will not cause the victim to drop an ear or a finger upon death (unless you kill them while detected.)

Behind the scenes

 * The "sandman" is a folkloric character who sprinkles sand in the eyes of little children, causing the rubbing of the eyes that is a sign of tiredness.
 * Mister Sandman is also a song, sung by The Chordettes, a mid 1950s - early 1960s Singing Quartet.

Bugs

 * It is possible that while murdering the victim, they will wake, stand up and become hostile towards the player, however, they will still die after the murdering animation is complete. It seems that when the character being killed starts attacking the player, no damage will actually be dealt by them.
 * It is still possible to perform Mr. Sandman kills on Kenny from the Point Lookout add-on and Sally from the Mothership Zeta add-on after patch 1.5.