Everybody who doesn't do drugs needs to get out of this thread. I regularly see a psychiatrist, who I basically view as a drug dealer who pays taxes. He gives me amphetamines so I become a person my school is more interested in. (Also so I can drive around without worrying about being like hey a bird! or I love this song! and running into a ditch)
Ya'll can preach about how we're shortening our lives or whatever (I hope I don't damage my CNS in the long term, knock on wood) but as a person instructed by society to regularly take drugs which have such a dramatic affect on who I am and what I do, I have two cents to share here. Firstly, the difference between what we call a "drug" and what we call "medicine" is a political one. If a kid around here were to take some MDMA and die it would be all over the news. If he were to take a few too many paracetamol and die, nope, just a statistic, nobody wants to hear about it. It's all fear and ignorance.
If you "don't do drugs", and feel the need to tell people who do not to, you're full of shit, and need to stop and think. I would argue that drugs are a fundamental part of what it is to be human, and if I still had my faith I'd say its your God-given right to get high and love it.
I'm going to answer the opposite question (BEST DRUGS!) and say that my forts run smoother when I'm on adderall (amphetamine- helped the nazis conquer europe so fast, keeps flight crews awake right now above the middle east..) , which is more or less every time I play. I'm more inclined to do things like reorganize all my 200 dwarves so as to be more efficient.
A close second is being stoned, pretty obviously. Video games and ganja go together like PB&J, and dwarf fortress has the benefit of not requiring accurate depth perception or fast reflexes. Your fort mode enjoyment is directly proportional to how much crazy shit you come up with, and when you're baked someone I know told me you'll be more inclined to do stuff like create a giant magmafall just for the hell of it. Furthermore, you'll see the whole thing in your head and will enjoy every minute of it.
EDIT: If you're an impressionable teenager reading this, I would like to emphasize that breaking the law is still a really bad idea (you really can't fight the state), and that you have your whole future ahead of you, don't be fucking around. That is all.