Staggering Blow

 
Prerequisite(s): Improved Critical (Unarmed or Bludgeoning Weapon), Power Attack, Heal 3+ ranks, Str 13+, Base Attack Bonus 12+
 
Benefit: Whenever you confirm a critical hit with a melee attack that deals bludgeoning or nonlethal damage for which you have the Improved Critical feat your opponent must make a Fortitude save (DC 10 + 1/2 your level + your Strength modifier) or be stunned for one round.
 
Special: A fighter may select Staggering Blow as one ofhis fighter bonus feats.
 
Source: Dragon Compendium