Negotiator (Fallout Supplement)
From D&D Wiki
Being a very skilled negotiator. Not only can you barter better than the best of them, but you can talk your way into or out of just about anything.
Prerequisite: Charisma 14+
Benefit: You gain a +2 to Bluff and Diplomacy skill checks, you also receive a bonus of 10% to buying/selling when Bartering and the maximum benefit is 60%. Note if the merchant your are dealing with also has Negotiator (and what good merchant wouldn't?) then this bonus is lost.