The Hammer Punch exercise works your shoulders and biceps.
On this exercise, you'll start with your palms facing forward. Take them up into a hammer curl and then you're gonna punch to the right and then punch to the left. Bring them back down, take it up, right, left and back down. After completing the designated reps, to challenge yourself, do quick 20 punches to one side and then quick 20 punches to the other side.