Over the years I have developed an allergy to Brazil nuts. Ugly stuff, my throat closes up, and I can't drink beer to wash down the mixed nuts at hand. Word to the wise, if your tongue starts itching and you have difficulty swallowing, don't eat more, bad things are about to happen to you. Anaphylaxis sucks.
Prior to those days, though, I would use a standard ol' vise type nutcracker. Always seemed to do the trick