Staggering Blow( Dragon Compendium)
[Fighter Bonus Feat, General]
You are capable of delivering devastating strikes in melee combat, and when you land a critical blow, opponents seldom recover in time to fend off your attacks.
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.
A fighter may select Staggering Blow as one ofhis fighter bonus feats.