Bear Fang

 
Prerequisite(s): Weapon Focus (Dagger and Battleaxe, Handaxe or Dwarven Axe), Power Attack, Two Weapon Fighting
 
Benefit: If you hit a creature with both your axe and your dagger in the same round, you deal normal damage with both weapons, and you can choose to immediately attempt to start a grapple as a free action without provoking an attack of opportunity, as if you had the improved grab ability. No initial touch attack is required. If you succeed on your grapple attempt, you drop your axe, but you immediately gain an additional attack against your grappled foe with your dagger at your highest base attack bonus (with the normal -4 penalty for attacking in a grapple). In subsequent rounds, you can use the dagger to attack while grappling at the normal penalty.
 
Source: Complete Warrior