Impact

This special ability can only be placed on melee weapons that are not light weapons. An impact weapon delivers a potent kinetic jolt when it strikes, dealing damage as if the weapon were one size category larger. In addition, any bull rush combat maneuver the wielder attempts while wielding the weapon gains a bonus equal to the weapon's enhancement bonus; this includes all bull rush attempts, not only those in which a weapon is used, such as Bull Rush Strike, Shield Slam, or Unseat.