Legalize recreational marijuana and industrial hemp, so we don't have to subsidize farms to not grow anything, and we can tax recreational marijuana, I think most of us who are smokers would not mind paying between 5-10 dollars per 3.5 grams of marijuana bought.
President Obama has also said that marijuana is safer than drinking alcohol.
Also with industrial hemp, we have renewable energy and would have less of a reliance on foreign oil, we can create hemp plastics, and clothing.
100+ years of prohibition is enough.