I know I must have done quite a few petty things to annoy an arsehole or several over the years but I'm coming up blank right now, so, instead here's a favourite from someone I worked with decades again and is so genius that I've never forgotten it.
So, work colleague is going to a party with a male friend of hers. The party is being held by a woman who desperately wants to get it on with colleague's male friend. Grand, colleague has no fucks to give about that as he and she really are just friends. Get it on woman, however, has decided that colleague is competition so decides to pretend to forget colleague's name and keep asking her to repeat it. Colleague has a really easy to remember the name, let's call her Sarah, so it's clear that this is some passive-aggressive bullshit move on the part of Get it on woman.
The evening draws on and it's really becoming deeply annoying, so, the next time get it on woman asks for the twelfthy-millionth time "Oh what was your name again, haha, I just keep forgetting!" Colleague said in quite a loud voice and into her face "Bunty!".
Get it on woman's face is a picture of "What the fuck do I do now!" and my colleague had the smile of the cat that got the cream. It was silly, petty and hilarious. Best of all, colleague's male friend thought that get it on woman was a bit of a twat because of her behaviour and get it on woman never got to get it on with him. If she hadn't played the arsehole all night she and he might have ended up together but she blew it.