Lateness regarding class. I understand that students can sometimes be late to class, but I don't understand why a person could be 15 minutes late to class EVERY DAY!!! What do you have that is so important that you have the need to interrupt class after we're just getting started. If you're apologetic about it, I may cut you some slack... but don't count on it.
"Kiss Goodbye"s. You will be seeing a person in four hours. No need to kiss them six times, then hug them, then kiss them again, then hold their hands for while, then leave, then say, "I'll see you at lunch." No need. Be cool. Just be cool. A peck should suffice.
Wrong side of the sidewalk walkers. Get out of my way. I'm going to class. Why are you making me walk in the grass? There's no need to walk 4 people across. Next time someone does this, I might have to shoulder them.