My ire is reserved for people who ban a thing just because they don't like it, without any legitimate, believable explanation as to how banning the thing would lead to a better game.
I find this odd. If I dislike a thing enough to ban it, it stands to reason that the game I'm DMing will be worse if it includes that thing. Who wants a grumpy DM? (At the extreme, the game might not
exist if I dislike it enough and for some reason I'm not "permitted" to ban it.)
I won't allow smoking in my house (we play all games in my game-room), and if I really had my druthers, there'd be no smokers in the game. Smokers
stink. Smokers waste time with periodic smoke breaks. Smokers are a pain in the butt, when it comes to gaming.
On the other hand, I don't mind drinking or recreationals at the table, or a bong-break during a session. Like others, I'd have a problem with truly
drunk or truly
baked players. (Been there. Went like this: "You see a staircase going down." "We go down the staircase." "There's a door, and a staircase behind you going up." "We go up the staircase." Funny to me (I was stoned), but not real considerate of the DM.)
I hate playing games without a stable group. I read many posts about how folks have "seven players, any four of which will show for a session," and it makes me wince.
I dislike playing games where I can tell the DM is just winging it. I don't know how to explain, exactly, except to say that this is about as appealing to me as sitting around a table and taking five-minute turns telling a story. (If I can't tell the DM is winging it, no problem.)
I won't play in a game where the DM routinely fudges die rolls in favor of the players. Same feeling as above.
Having read the rest of the thread and been reminded of some stuff:
I won't play in or run games with evil PCs. I won't play in or run games in which the PCs do things to one another that would lead to fighting.
I don't exactly
prohibit cross-gender PCs, but I strongly discourage it. (Yes, yes, I know ... I'm a monster. Whatever. Rraw.)
I snap at people who do things like play on their iPhones. I honestly don't mind the occasional text, or the occasional phone call, and if your PC is truly out of the action, I don't mind you playing Bejeweled. But if you're just bored,
get involved.