Mephedrone?
I keep telling myself "never again, never again, never again." The problem is, I knew all about how bad it is before I ever tried it, and then it was offered to me for free, and I did it, and then kept doing it multiple times a week until I ran out. I never did a whole lot at once, maybe 1-200mg in a night because that's all I ever needed. My original stash was maybe 2.5g and lasted under a month. The fact that I couldn't resist doing it scared me. Even now, I want just a little bit (maybe one gram) just to hold on to... for my wedding night or something. But then again, I know it's better to not go near it. ever again.