This is a great move for building a strong back!
While grabbing a dumbbell in one hand, bend forward placing your opposite knee on a bench, keeping your back level with the ground. Keep your non-working hand on the bench for support. Start with the weight down by your side keeping your palm facing your body. Steadily lift the dumbbell by your side (the motion is like that of starting a lawn mower) concentrating on your back doing the work rather than your bicep. Keep the motion slow and controlled.
No gym? You can also perform this exercise without a bench. Get into a lunge, placing your non-working forearm on your thigh for support. Perform the motion the same way. This is a great way to work on core stability as well.