People talking, texting, whatevering in the cinema during a film. Once the production company logos come up, the movie has started and you just shut the fuck up.
Another one that's becoming way to prevalent lately are steelbox editions of blu rays or special packaging for tv-series where the back with the info is a loosely glued on piece of paper you sometimes have to rip to access your discs. Seriously, that info is important, so why would I want to throw it out. It's even more annoying when they have cardboard versions of it, because the paper ones you can at least fold and place inside the case. My GoT season 7 box is the latest perpetrator.