You are skilled at attacking your opponents' weapons and shields, as well as other objects.

Power Attack, STR 13

When you strike at an object held or carried by an opponent (such as a weapon or shield), you do not provoke an attack of opportunity (see Sunder). You also gain a +4 bonus on any attack roll made to attack an object held or carried by another character.

Without this feat, you provoke an attack of opportunity when you strike at an object held or carried by another character.