Guardian of forever encounter. It lets you re-live the vault dweller for a few minutes. Spawn into the fight with the master, he has 1 hp left, you have a plasma rifle in your hands and shoot him. There are a few corpses lying around (Nightkin) one corpse has a stealthboy and a 100/100 laser rifle, the other has a stealthboy and a 100/100 plasma pistol. You can search the master's corpse and it has a 2x 98/100 gatling lasers. (Much less valuable to a player when not 100/100). This would be quite a profitable encounter. Seems cool, right?