Martial Initiate

You have trained in a specific form of martial combat in your free time to enhance your adventuring skills. This feat grants you one weapon mastery in addition to one of the following martial benifits:

Fighter: You gain proficiency with martial and simple weapons, as well as an extra weapon mastery. 

Rogue: You add your proficiency bonus to your attack rolls while Hidden, and you can add 1d4 damage to an attack you make while Hidden a number of times per Long Rest equal to your proficiency bonus.

Barbarian: You add your Constitution modifier to your unarmored AC, and you can add 1d4 damage to a Strength based attack a number of times per Long Rest equal to your proficiency bonus.