"The Game" and "Marco - Polo". One year I was on the second floor mezzanine at the Hilton and the person next to me, quite literally yelled in my ear at the top of their lungs POLO!
It may not be an annoying thing, but something that does peeve me no end. People NOT ATTENDING GOH PANELS. The one thing that , for me at least, defines a convention, is being able to meet celebrities that I couldn't meet at any other time. So, I go into the panel for Cynthia Martinez (English voice of Lina Inverse from the Slayers movies and Sora Naegino from Kaliedo Star among others), and there are maybe 20 people in a room large enough to hold 200. They didn't even fill the first two rows. I can hear tons of people in the area outside the doors making noise, yelling, screaming, I look outside the door and 90 people are just loitering around talking to one another. WTF! How much did we pay this person to fly out here, provide them an escort, pay for their room, and 20 people show up to see them out of over 1000, that is just wrong. I went to her autograph session later in the day, 150 people easy.
I don't know, maybe I am just showing my age, but people who come to the con and spend the entire day in the gaming room hogging a game that they own at home, or playing an RPG. You payed admission so you could do this?
I feel terribly uncomfortable when a really young female asks if she can hug me. I never know what to do with my hands. I usually try to hold the small of the back in a gentle squeeze, but my arms are long enough to grab my own elbows with each hand and still have this "little kid" not feel any pressure. When you consider that I am probably as old as, or older, than their parents, you wonder if the same kid would ever even THINK about hugging their dad that way. I doubt it.
My daughter was in a mascot costume (Silver the Hedgehog) and had very limited visibility. She was mass glomped to the point of almost falling down, and then actually picked up off the ground. It scared the (bleep) out of her, she couldn't even see who was holding her. My wife was her handler, and they actually pushed her out of the way. Now THAT is rude.