Two good uses for a wand of cancellation:

  1. Zap it at a bones pile, having first removed anything you do not want to be cancelled. As well as uncursing things like unicorn horns and luckstones, making them useful, this will convert a cursed bag of holding (which may well be too heavy to lift) into an uncursed bag of holding. The contents of the bag will not be cancelled and will not have been cursed when the bones pile was created either.
  2. Collect junk potions and scrolls, and every so often, drop them and zap the pile with your wand of cancellation. Then make the resulting water holy and write on the blank scrolls.