You can maximise bludgeoning effectiveness by using an old Eko Ranger 6 - Nice guitars - They were fitted with a large (5 inch cube!) block of wood which helps to give momentum in ones pre-bludgeoning swing.

However these are nice instruments and they probably don't deserve it.

Any Yamaha keyboard from the PSR series. They deserve it.

My friend bought a korean Strat. He took it home played it for an hour or so. Then he placed it carefully in the centred of a roaring fire and burned it. He has "issues."