You can respond to any number of opponents who let their defenses down.
Prerequisites: Dex 21, Combat Reflexes.
Benefit: There is no limit to the number of attacks of opportunity the character can make in one round. (the character still can’t make more than one attack of opportunity for a given opportunity.)
Source: Standard Reference Document under Open Game License v1.0a, which updated this feat originally published in the Epic Level Handbook, page 57.