Right, GHB is an interesting one. It's always fascinated me how most recreational drugs are a wonderdrug for at least one medical condition. There are a couple of exceptions of course. Like synthetic cannabinoids. But even ethanol can be used as an antidote for methanol poisoning.
For me it's amphetamine. I have severe dehabilitating ADHD-C and lisdexamphetamine has completely changed my life.