Tunnel Snake outfit (Fallout 3)

A Vault 101 Jumpsuit covered on the torso by a Leather Jacket (snake emblem on the back, can be seen on Butch DeLoria or the Tunnel Snakes before taking the G.O.A.T.).

Location
During the Escape! quest, you can either kill Butch and his mother and loot this jacket, or help him (either way) and he'll reward you with this. You can also obtain this by killing Butch in Rivet City after completing Trouble on the Homefront.