Tea/ coffee rounds - the source of so much angst, so much passive aggressive huffing and so much bad feeling. If you want a drink, GET ONE. People's thirst levels and workloads rarely align so there's always someone who thinks they make more rounds than everyone else, and always someone who only wants 2-3 cups a day but feels like they need to have one hourly to keep the rounds even.
When I am Queen of the Universe, these will be one of the first things that gets banned.
Meetings - people cancelling at the last minute when I've travelled a long way or organised other things around it. Also, people who don't follow the agenda in long meetings. It's there for a reason, stick to it and we all might get out on time
Lunch - people who chat to me, people who ask me to get them something at the shop instead of using their own lunch hour to get it (it's always something complicated as well - just fuck off!), people who make huffy comments about people's professionalism because they take their lunch (the people doing the huffing are never, ever the ones who are the most productive)
Useless office sniping. Everyone works here, everyone needs to be able to get along at a surface level and work effectively. If you can't do that, perhaps you need a new job
On the other hand I can zone-out loud people, don't mind smelly food (as long as it's in the designated canteen/ dining area and not at your desk), and couldn't care less who's in 5 minutes later or out 5 minutes earlier or takes a lunch break of 1hr 5 mins on ocassion as long as they're productive.