6. People Having Sex
Sounds bizarre, but it happens. Whether through sheer boredom or just a need to be exhibitionists, some people feel compelled to get it on while the film's on, and you might just be unlucky to be near it when it happens. It's very hard to concentrate on the subtleties of a conversation when people you don't know are moaning and grinding in the row next to you, and getting naked isn't going to make the film any more exciting. If you must get naked while watching a film, do it at home - no-one else wants to see you with no clothes on.
5. People Kicking Seats
As if you weren't uncomfortable enough already, you might just be sat in front of some idiot who thinks that kicking seats is amusing. Even if it's a hard-backed chair with some kind of padding, you can still feel it every time his heel or toe connects with your back. You're doing everything you can to resist turning around and punching him, and all the while he's laughing like it's the funniest thing ever. It's not. Grow up you halfwit.
4. Shoe Removal
If you're watching a film in the comfort of your own home, you can do what you like with your shoes - you can even fling them at the screen if the film's that bad. But in a cinema, you can pretty much guarantee that people haven't paid a lot of their hard-earned money for the privilege of smelling your feet. Smell-o-Vision is a thing of the past, and your sweaty soles takes us out of the experience. Keep your shoes on or stay at home.