I've pretty much been able to abstain from using any substance by changing my environment. There's a special place in my heart for almost any of the drugs I've tried or used on a regular basis, but I've found that not having said drug around or being in a setting where there's no association with it eliminates any cravings for the most part.
Personally & psychologically, ethyl alcohol to me is the ultimate poison. Being dependent on it is not far off from having an eating disorder - there's simply no avoiding it in the western world, especially if you had a relationship with it in the past. I broke up with that motherfucker and haven't had a drop in 2.5 years but I'm still heartbroken. Using the changing environment strategy has left a big hole in my social life (including enhancing work relationships). I still feel as if I'm missing 80% of the social interaction I had when I was drinking.
Nicotine kicks my ass too, mostly psychologically. I am disgusted by it. The smell, the cost, the phlegm, the stigma. The good thing is that society has come to look upon us smokers as drug addicts, forcing us into crammed areas outside buildings shivering in the freezing winter and taxing the shit out of our addictions. I've quit many times -- sometimes for years -- and every time its either due to a major change in environment or an illness that makes the stuff taste like total ass.
So in summary the 2 legal ones to me are the most addicting.
As for some others...
* Cocaine - if its there I'm snorting it until its gone. Put my face in that powder, New Orleans beignet powder sugar style. Makes me feel like super man.
* Crack - 1 night was enough for me. When I hit rock bottom I ended up randomly hooking up with some homeless dude and smoking it all night. God knows how many rocks we went through. When we ran out and I went home the dude stole my car battery and some other worthless shit out of my $450 junker car. Tyrone Biggums, is that you?
* bk-MDMA / Methylone - unlike E, this stuff is moreish as hell to me. Its very cocaine like imo.
For some reason I'm just not into other downers. I have stockpiles of benzos, Seroquel, Tramadol, and easy access to several kinds of opiates. They're all very powerful tools but from a recreational standpoint they're just not for me. I'm very socially anxious and have low self-esteem (hence the love affair with alcohol), but these drugs just dumb me down and don't even seem to feel that good. Well, I guess my 2 year almost daily Kratom usage might be an exception, but deep down I actually didn't enjoy the stuff...it just numbed me out and kept the sorrow from missing alcohol at bay.
I usually abide by the "try everything once" philosophy. After reading the responses on this thread though I can say for certain that I'm never going near MPDV, Meth, or heroin-strength opiates. There's an instinct in me that tells me I should stay clear of GHB, due to its similarity to alcohol. I recently got my hands on some K too, which I hear could be problematic. Guess we'll see how that goes.