that parenting is all about throwing shit at the wall.
As for the idle threats, well, it's up to you how idle it is. You really CAN give away their favorite toy to Goodwill or something. That would send a powerful message. I know we want to protect our children from pain and treat them tenderly but sometimes you have to be tough and inflict psychic pain to deliver a lesson. In the overall scheme of things, losing a beloved toy is not that great a tragedy but might trigger their "pain avoidance" instinct and cause them to be more cooperative in the future.