Sometimes this kind of question can be really funny to answer. What does someone do that really IRRITATES you! DRIVES you NUTS! Makes you want to just SCREAM!? I will start, of course... What drives me nuts the most is when you ask someone to do something really simple because you are busy with something else, and they only do it half way or do a lazy job at it...causing you to not only fix their mistake, but finish what they started.