Here’s one where the price just has to be about right. You invest a few dollars in some Norwegian rats — the big, dirty, mean ones. The idea is to get males and females. Put them in some well-screened rabbit hutches. Feed them on garbage and swampweeds. These rodents are cheap to keep, and they multiply quickly, and they make people really unhappy.
Ask a New Yorker about the Rat Raids of summer 1979! I am sure the imaginations of many readers have already figured out creative things to do with all those rats. Good old Willard, revisited!