Shoulder Circles Exercise
I used to use this mainly for shoulder endurance, very useful when I was boxing for having the endurance to keep your guard up at all times. A little difficult when you first start but you'll build endurance very quickly with very little muscular pain after.
Not that difficult to do, just put your hands out to the sides or directly in front of you then draw circles with your hands in the air. Try going one way then the other, then small circles, then big circles, some slow and some fast.