1) MPDV. i have only tried this drug once and that was enough. My god, i thought I had done myself irrepairable mental and physical harm. My heart was going bezerk, I had chest pains, vomitting, paranoia, anixety, numb limbs, headache, and bad bad insomnia. When my heart was beating so I fast and painfully I came very close to calling an ambulance. However, its one saving grace was that i was still horny as all hell, and sex was still really good.
2) Methamphetamine. Heart is racing, you can't sleep, your in pain, your thoughts go into all kinds of anxious, distrubing and paranoid spheres. Plus the comedown lasts a few days.
3) Alcohol. These have gotten a lot worse as I have gotten older. What is particularly bad is I get bad depression and anxiety on a hangover these days. And as someone said before, there is nothing worse than getting blind drunk, and doing something really embarrassing or wrong, and remembering it the next day.