There is no "I" in tank team.
Actually, there might be a couple of pet peeves coming out today.
1. When your raid leaders go on vacation and someone else steps in to handle a run, please don't bitch at her for something that happened on that run weeks ago that she had nothing to do with.
2. Oops, I just out-threated you.
My biggest pet peeve from tanks is this. Fights that aren't tank-swaps, but they are still swapping because there's not enough team work. Sure, it's a farm boss and a tank swap isn't a wipe, but it's obvious there's one player who wants to be the star of the show even though we've told him that he's the third tank (when you have 24k hp unbuffed to tank ICC25, I feel the correct response is grateful humility, not taunting off the other tanks and calling it an accident).
I've been the super undergeared second/third tank before. It's hard to pick up aggro off someone who has three times the attack power and mitigation than you do (especially if you're still gemming for def cap). You have to do something snotty like taunt and pretend you didn't.
If it's not a tank swap, don't take the boss. If it IS a tank swap, no need to taunt before the swap time. There's a reason we agree on encounter specifics like "X stacks" or "X boss cooldown" to swap, and not "I'm bored and I want to see the boss swinging at me instead". And if we ask you to DPS, the correct response is "ok, let me switch" and not "ok but I'm going to stay in tank spec and gear in case something goes wrong".
No, you're not.
I'm sure there is such a thing as an accidental out-threat, but I don't believe it happens more than once. Certainly, not seven times in one fight.