Arnold press:
Grab a set of dumbbells and bring them to shoulder height with arms bent and palms facing the body. Gripping the dumbbells as tightly as possible, press them overhead, rotating the dumbbells until the palms are facing forward at the top of the press. Pause, and then slowly lower the weight, reversing the rotating so that the palms end facing the body at the bottom of the press.
Do not relax your muscles during all the exercise.

Arnold press.