Weed. People are retarded if they say it isn't addictive. It just isn't addictive in the same way cigarettes are. And also, screw anyone that says that weed isn't harmful to your life. I know only a handful of people who can live their life and also smoke weed without any problems, and they all have life styles that work well with being able to smoke weed.For example, one of them runs his own business, and he doesn't smoke while working.
I'll probably never stop smoking entirely, but it became a problem and I refuse to let it hinder me, so I pretty much quit entirely. I only smoke cigars because I really love to smoke things, be it hookahs, vaporizers, joints, and I don't buy them very often, so they don't tend to be a problem.