Lug-Nut

 is a Raider who appears and confronts the player as soon as they loot the Naughty Nightwear as part of the unmarked quest Grady's Package. He wears a random raider armor and carries a random weapon (hunting rifle, sawed-off shotgun, or  assault rifle)

Upon your taking the Naughty Nightwear, Lug-Nut will demand that you give it to him. If you refuse to give it to him, he will become hostile and attack you, or you can just intimidate him with a high enough speech skill. He can be enslaved with a Mesmetron. However, if you just kill him on sight, you do not get negative karma even though he is marked as friendly.

If you successfully scare him off with Speech, he'll hang around the Marigold Metro Station tunnels, and may be attacked and eaten by the resident Giant Fire Ants. If he spawns with an assault rifle, he does a fairly decent job of killing any ants that respawn near wherever he's wandering. However, if he appears with a hunting rifle or sawed-off shotgun, he'll promptly be turned into ant food if he ever runs into any of them.

Lug-nut is also mentioned by Sierra Petrovita when asked more about Ronald Laren. She will start talking about how tough Ronald Laren is and will mention Lug-nut and two other raiders. The two unknown raiders were killed by Ronald Laren, who then punched Lug-nut in the face. Lug-Nut probably only survived because Ronald was using his signature weapon, The Kneecapper, which only has a two-shot capacity before reloading. Lug-Nut most likely made a run for it as Ronald was reloading.

Quotes
"I'm only gonna ask you this one time. Give me the Naughty Nightwear!"

Appearances
only appears in Fallout 3.

Bugs

 * On rare occasions, if you attack Lug Nut with a melee or unarmed weapon in V.A.T.S., a glitch will occur and you'll fall through the floor.
 * Lug-Nut can spawn with any Special Weapon or Power Armor. (Tested on 360, he spawned with Blackhawk and Tesla Power Armor.)