The Tenderizer (Fallout 3)

This special Sledgehammer, The Tenderizer, is located in Anchorage Memorial in the storage room with the broken door. The door can be fixed by finding the Door Component, but note that you need a Lockpick level of 50 to be able to open the safe in which the door component is stored in the top level of the building. A Repair skill of 35 or higher is required to fix the door with the help of the component. Without the component a repair skill of 95 is required.

You can repair The Tenderizer with other Sledgehammers.

The Tenderizer damages enemy armor on each hit by 5 points. This is the only such "enchanted" weapon in the game.

Its purpose could have been to "tenderize" mirelurks.

YouTube video for location:
 * http://www.youtube.com/watch?v=sFxSflafnWI