How about one in the same vain as Crack the Shell for but weapons?
Bend the Blade
You can spend 1 ki point after you make an strike that hits to attempt to break a foes weapons, hands, or claws. The attacked creature must make a Strength saving throw or take a -2 penalty to one of its weapons. A creature may only be under one of this effect at a time. The creature can have its weapon repaired normally, through the use of a mending spell, or in the case of natural weapon have a healing spell cast upon it. A foe can pick up an identical copy of this weapon and be free of this penalty as well.