Riposte

Riposte [Warrior]
Prerequisite: Weapon Finesse, Expertise, Melee BAB >= 6.
Benefit: After deflecting an opponent's blow you can quickly attack while the enemy is over-extended. When you are not surprised, at most lightly encumbered, and wearing at most light armour, you may make an attack of opportunity against an opponent who is beside you and tries to attack you in melee and misses.