Lists have a reputation as the Web's junk food. Even so, millions of people consume them with abandon which is why so many sites publish so many of them. You don't have to feel apologetic about digging into the daily reader-submitted top-10 lists at Listverse. The best ones, including 10 Horrifyingly Difficult Opera Arias and 10 Formidable Predatory Insects, aren't guilty pleasures they're entertainment that also happens to be kind of educational. Even the more offbeat examples, like 10 William Castle Film Gimmicks, aren't just empty calories.