You are a very skilled negotiator. Not only can you barter with the best of them, but you can talk your way into or out of almost anything. With this Perk you gain +10% to both Barter and Speech.”— in-game description, Fallout 2
+10% to Speech and Barter (Fallout 2; in unpatched versions the bonus is +20% instead) or +20% to Barter (Fallout Tactics). As with all skill perks, it's quite useless.