For me, it's the fact that people can't adjust their time schedules. If I have plenty of time, I have no problem letting someone go ahead of me and I ALWAYS select the correct security line (you know expert traveler, family travel, casual traveler) based on what I packed. I wear slip off shoes, I get a plastic baggie from the 1800 security stations where they have them and I make sure my passport and ticket are in an easily accessible pocket. WHY on EARTH can't other people do these simple things?
So obviously, that is my pet peeve (more an airport pet peeve than a travel one, I confess). What is your travel pet peeve? Because although I know everyone here loves travel, there must be some little things that get on your nerves....
Smelly travelers annoy me. Please just shower. I get it, you are a rugged backpacker, you're saving money, you're a rule-breaker, whatever. Just use some soap and water. You smell.