Grasp a plate with two hands. With a slight bend in the elbows and while keeping the back straight and shoulder blades squeezed together, slowly move plate in a slow "figure 8" pattern.
This exercise is a great workout for the upper deltoids. If you are feeling strain in your back, try holding the plate slightly closer to your body.
The key to this exercise is not going only part way with the rotation but do a full figure 8 making wide loops.