High Plains Drifter

 refers to an unmarked quest in Fallout 3.

On the top floor of Dickerson Tabernacle Chapel is a sniper called Drifter. He carries the Reservist's Rifle as well as the holotape for Oasis.

He is always hostile to the player and will attack the player once they reach the building. As he is on an unreachable ledge, he must be dispatched with a ranged weapon or grenades. Sometimes he might drop from the ledge to engage the player, allowing for more options to kill him. The real challenge is to kill him in a way that puts him in a lootable position as you cannot reach the planks he is on normally. However, even if the drifter is killed in the rafters it is possible to jar him loose with a nearby explosion.

Behind the scenes

 * The name of the Unmarked quest and the Drifter is a reference to the Clint Eastwood western High Plains Drifter. And this could also be a reference to high plains drifter by the Beastie Boys.

Bugs

 * Occasionally the Drifter will disappear after the player first encounters him. The drifter fires a few rounds before backing up and "falling" into the house. After his disappearance, any of the walls of the tabernacle bring up his health bar, indicating that he is "in" the woodwork. (confirmed PS3)