Two of my favorite anti-rotational movements are the traditional banded Pallof press and side-banded overhead Pallof press.

With minimal movement at the core, you can get a desired training effect with isometrics. Since isometrics have been shown to have a 15-20 degree carryover, be sure to train multiple points in the range of motion for best results.

Related: Rotation Training for Lifters and Athletes

Related: Big, Thick, Chunky Ab Training