All of them, but the more harmful ones should be regulated in various ways to minimize their use.
Well, I'm fine with outright banning stuff like bath salts and krokodil, but more or less this. (And legalization/regulation would probably crowd out the real grody stuff anyway.)
A sane drug policy would probably make it easier to get LSD than tobacco, for instance; it's mostly the weight of tradition that keeps policy as it is. Which is not necessarily the worst thing in the world, but best for us to be honest about. I mean, alcohol is pretty harmful, but I support it being accessible far out of proportion to that (and do in fact use it pretty frequently myself) because it does play such a central role in civilization, and as such the product has evolved in so many diverse ways that are about much more than just intoxication.
