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.