Negotiator

You present a trusting personality that helps you get your foot in the door or push foes off their guard during combat. 

You have advantage on Charisma (Persuasion) rolls that involve starting negotiations of some kind. This is up to DM discretion, but typically includes requesting to speak with people in positions of power, avoiding a fight, or convincing people to parlay with each other. You do not gain advantage on all Charisma (Persuasion) checks during a following social interaction, however. This feat would grant you advantage on your roll to convince a guard to let you speak to their captain, but not on your roll to convince the captain to release your party members from jail, for example.

Additionally, this feat allows you to distract an enemy during combat by speaking to them. Choose an enemy that you can see, that can hear you, and that can understand your language within 10ft of you. If an ally of yours attacks the creature before your next turn, they gain advantage on their first attack roll against the creature. This ability can only be used once per combat encounter.