This exercise from Men's Health will tax your whole body. The abs workout exercise called the "Turkish get-up" will especially tax the core muscles and shoulder muscles as you progress your way to heavier dumbbells.
Lie on your back with your legs straight. Hold a dumb-bell in your left hand with your arm straight above you. Keeping your elbow locked and the weight above you at all times, stand up.
Move your legs and right arm underneath you to push yourself up. Still keeping your left arm straight and the weight above you reverse the motion and return to the starting position. Complete your reps on this side before switching to the right arm to finish your set.
This exercise will tax the whole body, especially the core and shoulder muscles as you progress your way to heavier dumb-bells. Keep a training partner close by who can catch the dumb-bell should you lose your balance.