1) Commute - wasted time and energy sitting in traffic, plus added stress depending on amount of traffic. (not to mention all that gasoline!)
2) The walk-by - trying to get work done when anyone can just saunter over and ask you a question, or just shoot the sh*t.
3) Noise and smells - people playing music randomly, loud conversations, YouTube videos, someone eating a smelly burrito, chinese food
4) The cold starter - someone has a cold but feels fine or wants to show they got guts, spreads the cold to 50% of the office.
5) Constant trivialities - walkby hellos, lunch anyone?, who's driving?, peeing next to someone in the bathroom stall
Anything else to add?