[Edi]

All the constructs are lifeless. In addition to them, it would afect things like the Sphinx, Oracle, Monolith and all lifeless undead like Lich, master lich and mummies. Crusherknack causes 20 AN damage in addition to the normal damage of the weapon it is attached to, but the secondary damage only affects things that are lifeless.

As far as magical weapons/armor, I would not be so quick to make blanket statements. Weapons and presumably also armor have various hidden fx flags, such as fx_iron and fx_wood. So for example Rust Mist would leave iron weapons and armor corroded and useless (hello, MA Ulm), but would not affect such things as quarterstaffs and leather hauberks.

Unfortunately those effects are hidden and short of access to the source code, it is unlikely that they would be found out. This also explains what the extra columns in the DB are that are not used.