Arnold Press

1. Raise dumbbells to shoulder height, with palms facing your body.

2. Push the dumbbells above your head while rotating your wrists 180 degrees (so your palms face away from your body at the top)

3. Slowly bring the dumbbells to the starting position, while turning your wrists back 180 degrees so palms face in where they were for the starting position.  

Pro tip: This is more complex than a standard shoulder press, so don't be surprised if you can't use as much weight initially.