Push Up Plank Alternating Dumbbell Rows
Try this awesome core stability exercise. I see a lot of people who do this and allow their hips to rotate a lot and not really get the benefit of developing their rotational stability in their core.
When you try this, imagine you have a glass of water on your lower back and try not to let it spill. Find a weight that's challenging enough yet easy enough to focus on stabilizing your core. As always, use the mirror to check your form.