What irritates you?
This usually happens a few times a week with me, but for some reason, I get really irritated when people can't say a simple "thanks" or "thank you" when you hold a door open for them. If I physically stop and hold the door until you reach it, the least you could do is grunt. Ungrateful people I tell you. I'm just gonna start saying "you're welcome" even if they don't say anything.
So, what irritates you?