Hydromorphone
Methamphetamine
One of the strong barbiturates like Secobarbital, Pentobarbital, Amobarbital, or Sodium thiopental.
If ketamine is something you can actually be prescribed to use at home, I would take that instead of one of the bottom 2. I guess I'd keep the barb and drop the meth in that case since I can get meth pretty easily now but I can't get any strong barbiturates (I'll find a source online someday, I hope). Ketamine is hard to find. I can easily get other NMDA receptor antagonists online though.
And I don't want to have a medical condition requiring any of those. Would be nice if they'd prescribe meth as an appetite suppressant and weight loss drug to anyone who is really overweight and doesn't have a high blood pressure (if you take meds for blood pressure that control it well, you'd still be allowed to have it prescribed).
(I assume it has to be legal in my country to count).