Mister Sandman/Fallout 4

Mister Sandman is a perk in Fallout 4.

Effects
With the first rank, you are able to automatically kill any sleeping human by activating them while sneaking, and silenced weapons do 15% more damage with sneak attack criticals. The second rank increases this bonus damage to 30% and the third and final rank increases the bonus damage to 50%.

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.