Hammer's Edge

 
Prerequisite(s): Improved Bullrush, Two Weapon Fighting, Weapon Focus (Bastard sword, Longsword or Scimitar and Warhammer or Light Hammer, Str 15+
 
Benefit: If you hit the same creature with both your sword 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 fall prone.
 
Source: Complete Warrior