Voted Heroin, but if Methadone had be available that's where my vote would have been. Heroin is way more fun, and less therapeutic, in my opinion, but Methadone always delivered, I could manage my intake, and the price was right.
I really wanted to vote for DMT (my most profound highs, and most visually stunning, beautiful experience every time) but it's not a drug that I would use daily, and I can't function on it, and I like to be high always.
I came dangerously close to voting GHB (though I like GBL better, because it's stronger), G + crystal = greatest high ever. Only drug combo that brought me that feeling I got on Christmas Eve back when I was 10 years old or younger. But I fall into a cycle of using GHB every fucking day, and the last time I came off a 3 week daily binge I was very scared. Felt like quitting a heavy heroin AND benzo habit at the same time... if drugs are going to kill me I'd prefer it to be in the form of a smack overdose, not a cramping-sweaty-seizure-y-mess.
Almost voted Cannabis because it's an awesome high, wide variety of highs, almost zero consequences, dirt cheap, no addiction potential, but who am I kidding? Heroin all the way and fuck the consequences (I'll say until I'm in jail again or kicking methadone cold turkey again).