I hear you on the being late thing. Though in my case, i wouldn't call it a pet peeve so much as a moral imperative. Being on time, especially in the military, is important. Not showing up on time is disrespectful. But maybe, I'm just a nut about it.
Pet Peeve, for me, was when people didn't return emails or phone calls. I never was one to "spam forward" email, so when I did send one, it was usual something I needed an answer on. In this same category, was the trend before I retired of support service (MPF, Finance, primarily) not answering a customer service phone line. Why bother to have it then?