Anvil of Thunder

 
Prerequisite(s): Improved Sunder, Power Attack, Two Weapon Fighting, Weapon Focus (Warhammer or Light Hammer and Battleaxe, Handaxe or Dwarven Axe), Str 13+
 
Benefit: You have mastered the style of fighting with hammer and axe at the same time, and have learned to deal thunderous blows with this unique pairing of weapons. If you hit the same creature with both your axe and your hammer in the same round, it must make a Fortitude saving throw (DC 10 + 1/2 your character level + your Str modifier) or be dazed for 1 round.
 
Source: Complete Warrior