Naughty nightwear (Fallout 3)

Naughty Nightwear is a set of leopard skin pajamas found during the quest, Grady's Package, in Fallout 3.

The outfit can be repaired up to 100% using various different "pre-war" outfits or up to 54% from an NPC.

Unmarked quest: Grady's Package
A humorous side quest (actually a sub-plot to the Nuka-Cola Challenge) involving the Naughty Nightwear can be found in Marigold Metro Station, near Grayditch.

Upon finding Grady's dead corpse on the upper level of the second large room, the player receives a recording of his last words. The recording describes the location of a key, in a fire hose housing (it's in a janitor's closet style room), and the location of the safe that has the package in it. The package is to be delivered to Ronald Laren in Girdershade.

When the player gets the important package it happens to be the Naughty Nightwear.

Trivia
Sierra Petrovita mentions a gang that wanted "to steal her stuff," led by "Lug-Nut or something." Lug-Nut is the name of the Raider who appears shortly after you acquired the package.

If the player has already spoken to Ronald Laren, it's pretty obvious why such an outfit is so important to him - to seduce Sierra Petrovita, who he is obsessed with.