Chin ups

Close-grip chin-ups

This exercise normally works the lats, but by focusing on the serratus contracting, you can turn it into a great serratus exercise.

Start in position to do a chin-up, with your hands close together and your palms facing towards you.
Pull your body up concentrating on the serratus contracting.
Lower your body back to the starting position.
If your working the serratus your body weight should be enough, but if you feel you need more weight you can attach ankle weights or a plate attached to a workout