People with kids who as you say don't even try to control them, I have been in a restaurant a few times now where kids have been messing around, jumping around and not sitting down and eating and their parents pay no attention.
Another is rude service. I get that not everyone likes working or even enjoys their job but would it kill to actually try and be polite?
Definitely people being overly loud and not doing anything about it. I suppose the next thing that would bother me is if the waiter/tress isn't paying attention, doesn't have a lot of tables to take care of and forgets to check in, especially when I want to leave. I don't get pissed or stiff them, but it's annoying.
Loud, even boisterous, talking, laughing, and stupidity by other customers.
Wait staff that walk around in a daze and actively ignore customers.
"Did any of you guys order the chicken special?"
True story, I have got up and gone to the waitress stations, got a pitcher of water, and brought it back to our table, and there have been times when nobody on the payroll noticed.
And I hate it when a waiter/waitress lies about something going on in the kitchen. I've working in the back of the house in more sorts of restaurants than most of the dingbats that work in these places have ever been in. I know how a cook line operates. Just tell us you forgot to put the order in, or that the prep cook was too drunk to fix it and the dishwasher just got a sudden promotion, or whatever the truth is, and be done with it. Don't go into "Oh, they're making sure it is Just Right!"