Here’s one from the master himself. The governator came up with this one during his reign as Mr. Olympia. It’s a great deltoid exercise and with the external rotation at the beginning of the movement it also is great for the rear delts.
Let’s start with dumbbells at shoulder level, with palms facing you. Rotate your hands around so that they are now facing forward, now press the dumbbells over head. Lower them back down to shoulder level and rotate back to the starting position.
Be sure to use a safe weight, and to keep your knees slightly bent. Breath out when pushing and breath in when not.