Panther Style

Combat Style

You can strike back at enemies who attack you when you move.

Prerequisite: Wis 13, Combat Reflexes, Improved Unarmed Strike.

Benefit: While using this style, when an opponent makes an attack of opportunity against you for moving through a threatened square, you can spend a swift action to make a retaliatory unarmed strike attack against that opponent. Your attack is resolved after the triggering attack of opportunity.

Source: Ultimate Combat