Quite possibly, screaming toddlers. At least the snakes kill you; the screaming, like Chinese water torture, just slowly drives you mad. I should know: a LAX->JFK leg I recently flew on featured more than 95 minutes of uninterrupted, top-volume toddler-screaming, so out-of-the-ordinary bad that several passengers got into heated arguments with the child's mother (certainly a rarity in the mind-your-own-business world of airline travel). Easily the worst flight ever, it got me to thinking about the Hawaiian 16-year-old who was kicked off a flight for suffering an excessively long coughing fit. A statement issued by Continental Airlines maintained that "the captain felt he was acting in the best interest of the passenger and other passengers on the flight." (Hmmm ... double-standard?)
Also, you may remember in January, a family whose screaming three-year-old wouldn't get in her seat for takeoff -- thus delaying the flight more than 20 minutes -- was kicked off the plane so the flight could take off. They then went on TV to complain. (Needless to say, the other passengers supported the captain's decision.) In another incident, a Northwest Airlines flight attendant pleaded guilty to giving a 19-month-old baby Xanax in apple juice to stop her crying on a transatlantic flight. Certainly a bit excessive, but it, and these other examples, raise a crucial question: what steps can be taken? Do passengers over the age of three have a right to some modicum of comfort on their flight? All questions ... just questions.