People talking while eating, people screaming at their kids, people text messaging and talking out loud at the same time. You know some people exaggerate when they scream at their kids in restaurants for misbehaving, I think they need to take the child outside to the car to give them time out or give them time out when they get home, yelling at kids or whipping them gets them no where...
Several things, but the most annoying thing would have to be people on their phones while spending time with other people.
Not necessarily over dinner, sometimes, just when you should be talking to someone face-to-face. Also, when places play really loud music and you can't talk to the people you're with; when there's nothing on the menu that I can eat; and people who laugh reeeaaaallly loudly - there's always one table...