Disintegration Finesse( Lords of Madness, p. 44)
A creature with this feat can use disintegrate effects to affect smaller, more exacting areas.
DEX 13, ability to cast disintegrate as a spell or use it as a spell-like or supernatural ability,
When the creature uses disintegrate on a target, it can elect to disintegrate only portions of the target. Against living targets, it still does the normal amount of damage, but any parts of the target it wishes to spare remain unaffected by the spell. The creature could, for example, disintegrate only a target's skeleton, leaving its skull untouched. It also can voluntarily reduce the amount of damage dealt. Against nonliving targets, the creature can use disintegrate to sculpt and reshape the object in any manner desired, as long as the result is no larger in volume or size than the original object. The quality of the result is determined by a Craft (sculpting) check.
If your campaign uses the Damage to Specifi c Areas variant rule on page 27 of the Dungeon Master's Guide, a creature with this feat can disintegrate a single part of a target's body, such as its hand, arm, head, eyes, ears, feet, legs, and so on, as long as the target is not killed outright by the damage caused by the spell.
A disintegrate effect destroys all of a slain creature, an entire object, or one 10-foot cube of nonliving matter.