Brutal Strike

 
Prerequisite(s): Str 13+, BAB 6+, Power Attack
 
Benefit: If you use your power attack to increase the damage you deal with a bludgeoning weapon, you can attempt a Brutal Strike. You must declare your intentions before making the attack. If the attack hits and your opponent tkaes damage, he must make a fortitude save vs DC = (10 + extra dam from Power Attack) or be sickened for 1 round. You can use this feat once per round during your attack action. This ability does not work against creatures that are immune to critical hits.
 
Source: Players Handbook II