Susana says the pallof press is one of her favourite ab exercises. If you don't have access to a cable machine at the gym, just attach a long resistance band like this one to a rig, a pole, or even a tree.
This is an anti-rotation exercise that really works your obliques. Your body wants to rotate in toward the cable or band, but your core has to work overtime to stabilize your body so that does not happen. Try it!