1) Neglecting to switch their mobiles off and then proceeding to answer calls/text/play snake or whatever the fuck else throughout the course of the movie. Recently I was sat between two rows of people, one of the people behind me received a call and then walked down to the row ahead of me and handed it to one of the people there so they could have some sort of conference call in the aisle!!!
2) Non-stop chatting. I don't mind this during the trailers, but, throughout the film? Fuck off.
See also: People who throw in 'wacky' one liners in a bid to spark spontaneous laughter from their fellow morons and dozy women who disappear to out of the screen for 15 minutes at a time before returning and loudly demanding a recap on what they've missed.
3) People who just won't stay still. How many times do you need to slash in a 2 hour period? I was sat next to a cunt recently who got up no less than 8 times at various points. He came back with food on at least 3 of those occasions. What the fuck happened to prior planning and preparation?
4) Returning to the food issue, don't buy the large popcorn containers...they cost about a tenner these days and you'll never eat more than a quarter of it...what you will do though is irritate the fuck out of everyone around you with your non-stop crunching and rustling.
Utter cunts, they really should be gassed.
That's not a deliberately over the top statement either, I would put them in camps and have them killed.