Sitting 10+ hours a day next to someone can either be a curse or a blessing. Either way, there is bound to be some trivial thing he/she does that make you want to smash your head through your keyboard. I've encountered the sneeze on their their hand then use your keyboard colleague, the low volume no headphone youtuber, the morning tuna eater, and the boyfriend texting giggler. I've been able to handle/stop them from these habits before any extreme measures had to be taken, but I'm curious as to what the worse thing you've had to deal with was/is.
My worst experience: My job had three months of training in a smallish room (one year ag)... The room was always hot, but we were able to request a lower temperature via a visible internal system. Every. Single. Person. thought that the room was too hot, except this one girl, lets call her 'Jane Doe'. Any time someone would lower it, she would null the request with a 'hotter temperature' request. I kid you not, she did this over 100 times. Our entire training grouptold her that she was the only cold one, so to piss off and wear something warm. As expected, she came in the next day with minimal clothing, and once again raised the temperature. On top of this - she would dump, not spray, her vile perfume in the middle of the humid hot room (of hers, apparently). We told her this was unacceptable as well, however as expected, nothing changed. She even got the name of the maintenance guy and would message him on the side to raise the temperature so we couldn't see her request.
(Un)fortunately, I knew from day one she wouldn't last long at our company. She made our 3 months of training hell, and in return, the gods deemed it that she be fired shortly after training. If you aren't capable of understanding the fair demands and relatively significant requests of others, or are just so oblivious and self centered, you wont succeed in (most) jobs. As karma had it, I by chance walked by her on her way out of the office (being escorted by HR)