I am VERY late to the party here, but with the difficult child in my life (not my child, but I lived with him for 15 months), taking his car keys away from him and refusing to return them to him for a month (and it had to be a month of sustained good behavior) actually worked. Of course, once he got them back, he went down the drain at high speed. But it worked while I did it. My experience was that that's the only thing that works, or might work: deprivation of a prized privilege/toy for a lengthy period of time, with the additional proviso that he has to behave during that period of deprivation or "the clock" (i.e., the period of deprivation) starts over at zero all over again. And you HAVE to absolutely stick to the initial period of deprivation that you claimed at the outset: no "time off for good behavior." And no allowance for angry/disrespectful harangues from him/her during that period--that too will restart the "clock." In the case of really hardcore difficult child, he/she might return to misbehavior immediately after the return of the privilege--difficult children are notoriously impervious to learning from experience--but at least it works while the consequence is being levied. Or it did for me, anyway.