Regulator duster (Fallout 3)

The Lawbringer Perk (accessible at Level 15) places the Regulator HQ on your map and allows you to visit Sonora Cruz, the head of the Regulators. The Regulator Duster is a piece of armor that you automatically get from Sonora Cruz for joining up with the Regulators.

You can also get it by having negative karma and killing then looting the bodies of the Regulators that come after you.