Imperator's Rebuke (3.5e Maneuver)

Your foes know not to let their guard down in your sight, lest you take advantage of their weakness to strike them down.

Whenever an enemy provokes an attack of opportunity from you, you may initiate this maneuver. Instead of making a basic melee attack, you may instead initiate a martial maneuver to make the attack of opportunity with. The maneuver must be a strike of 3rd level or lower that has an initiation action of 1 standard action, and must allow you to make a single melee attack. You must know the maneuver you initiate, but you do not need to have it readied, and it is not expended.