^ I've been guilty of that one, though usually only if I'm in one of my 'kill everything everywhere' moods.
But the only thing worse than crying kids is some of their parents. At least where I am, most of them are the epitome of trailer trash. Gods, and you wonder why the kids are brats...
And speaking of bad parenting, what about those people in the cafeteria that shout everything they say at people sitting right next to them, and then get mad at you when you ask them to keep it down. And every other word they drop an F bomb. Is it just me?