Bobblehead - Barter

 is a Fallout 3 item, a Vault Boy Bobblehead. It permanently improves your character's Barter skill by 10, to a maximum of 100.

Location
Found at Evergreen Mills' Market Bazaar, in a dark cave-nook, in the corner of the room to the right of Smiling Jack (trader). Jump over the work bench, it's on the right-most shelves.