Well, if I'm to really be honest, than I would have to say heroin. For about a month there I just wasn't getting high anymore, but then I switched connects so I got some of the magic back. But opiates are ever going to be the same unless I take a long break.
For some reason though benzodiazepines continue to work for me, even with a habit. The thing is that I actually have a lot more will power with them than the latter. I'm prescribed 1mg/day, but will often take 3-4mg/day (of clonazepam) and then not take any until I cannot stand it (which is around the 72 hour mark). Also, strangely enough, if I decide to continue to use benzo's, and have been taking 3-4mg of clonazepam a day, if I switch to alprazolam I can get off on half as much which I find strange as they're pretty much equipotent. Granted, clonazepam has a much longer duration of action, but the onset is pretty similar to Xanax IME if taken sublingually, and if its been 3 days, 1mg of clonazepam feels stronger than 1mg of Xanax. Doesn't make much sense.