Tavern Brawler

Source: Player’s Handbook p. 170
Ability Score Increase: Increase your Strength or Constitution by 1, to a maximum of 20. Accustomed to rough-and-tumble fighting using whatever weapons happen to be at hand, you gain the following benefits:

• You are proficient with improvised weapons.
• Your unarmed strike uses a d4 for damage.
• When you hit a creature with an unarmed strike or an improvised weapon on your turn, you can use a bonus action to attempt to grapple the target.