I'm a Ragnarok Online GM, so the number of people who do annoying things is astronomical. The way people PM me drives me nuts, I wish they'd just come out with the question, instead of spamming this over like five lines:
"hi GM"
"hi GM"
"GM?"
"GM can I ask"
It's like, just say hi, and ask the damn question. You don't need to call me GM, I know I am, I don't need reminding. If one person does this, it's fine, but when you have 7 people all doing it at once... argh.
It doesn't even say GM in my character name. If someone calls me by my rank, I'll call them by theirs, it's just friggin' rude. Then you get all the people who think they've been mistakenly banned or something, so they go to the forum to calmly post and get the issue sorted out. These posts are usually titled "F*** THE ENTIRE GM TEAM" and go on to threaten us and all our mothers, and don't even bother giving us their in-game name so we could find out why they were banned in the first place.
Or, I'll announce I'm going to do an event, and will announce the start in a minute, and I get a hundred PMs asking me if it's started. Or I'm doing Hide and Seek, and get another hundred asking me where I am. What?
I think GMing on any MMO is enough to make you cry.