In California, selling cannibas to a co-op you belong to as a patient could be a nice supplemental income. An Aerogrow makes it easy, and with six legal plants, you can grow at least 1.5 pounds every 90 days. I think it works out that you can make $10-15k/year for not much work.
That is not passive at all. You have to change the res every two weeks, plus be on the look out for any signs of stress (bugs, nutrients, and environment).
Then you have to process it, which a pound can be trimmed by a professional in about 10 hours. BTW you need to supervise them or do it yourself.
Then you get the hassle of dealing with the clubs consignment drama... Not to mention the stress of worrying about being robbed throughout the whole cycle.
I'd say it's probably the most unique idea in this thread, given that most HNers likely wouldn't normally think of dealing/selling drugs as being particularly creative.
And no, my wife would not let me do this :)