Whether automatic harpoon/spear guns are an engineering possibility.
It was originally phrased as a question, like "I wonder if automatic harpoon guns exist...". One of my know-it-all friends went crazy after I said that, and went on for at least 30 minutes about how not only did they not exist, but they were an engineering IMPOSSIBILITY, and that I was a moron for thinking otherwise.
whoops, misread... this didnt take place on AT. though, now that I am thinking about this i almost want to post and see what people think