People chewing with their mouths open or making a lot of noise when eating.

The loo roll being gone when I go to use the toilet, it's more that when I use up the loo roll I always make sure to grab a new one out after, but so many other people I know don't do this.

Flicking through channels during an advert break, this one winds me up the most tbh, mostly because it's pointless since nearly all the other channels will be on advert breaks too and y'know what? I don't actually want to miss any part of this show/movie I'm watching. Stop it.