All of the poll options are bad! However, the worst incident (not flight, but just a few moments of he**) was on a trip back from Europe. I cannot seem to sleep on long-haul flights. I had just drifted off to sleep and the person (old enough to know better; either never flew before or just did not think) was finished with the tray table and slammed it back into place. Not just a slight jar, but the entire seat was roughly smacked. I have neck issues (two spine surgeries on the neck - however, this was before the surgeries). Needless to say, I was now awake and would be for the rest of the flight. The person did apologize (quietly, more to themselves than to me). I can handle a crying baby (hopefully not a long-haul flight) but the bad bo, or illness, or several other options would not fare well with me. Luckily, I have not had them happen. Did have a kid behind us that kicked my seat for most of the flight. Mom did little when told.