The 1st level spell Break
School transmutation; Level sorcerer/wizard 1
Casting Time 1 standard action
Components V, S, M (a twig)
Range close (25 ft. + 5 ft./2 levels)
Target one Medium or smaller object
Duration instantaneous
Saving Throw Fortitude negates (object); Spell Resistance yes (object)
You can attempt to break or at least damage any one Medium or smaller object within range. If the target fails its Fortitude saving throw, it gains the broken condition. If cast on a broken item, that item is destroyed on a failed save.
Can you cast this on an NPC's sword while in his hand? If so, what save does it get?
(object)
The spell can be cast on objects, which receive saving throws only if they are magical or if they are attended (held, worn, grasped, or the like) by a creature resisting the spell, in which case the object uses the creature's saving throw bonus unless its own bonus is greater. This notation does not mean that a spell can be cast only on objects. Some spells of this sort can be cast on creatures or objects. A magic item's saving throw bonuses are each equal to 2 + 1/2 the item's caster level.
So if it's non-magical and unattended, it gets NO save. If it's attended (a sword held by someone) then it gets the user's Fort save (but if it is a magical sword it has its own Fort save and uses whichever is higher).