Fists of Iron

 
Prerequisite(s): Improved Unarmed Strike, Stunning Fist, Base Attack Bonus 2+.
 
Benefit: Declare that you are using this feat before you make your attack roll (thus, a missed attack roll ruins the attempt). You deal an extra 1d6 points of damage when you make a successful unarmed attack. Each attempt counts as one of your uses of the Stunning Fist feat for the day.
 
Source: Complete Warrior