My main pet peeves revolve around phones.
Late callers: When I was young not everyone had a phone, it was drummed into me that you should never phone someone after 9pm unless it was an emergency as most people would be getting ready for work the next day.
It drives me wild when I get called after by people who aren't close to me, my last landlord would phone as late as 10:15 for trivial stuff, Grrr
Mobile phones in general: With the proliferation of mobiles we are all expected to be on call 24/7, if you are having a conversation with someone & they get a call they will interupt you to answer, I feel like butting in halfway through their phone call to show them how rude that is!
If you want to be left in peace then someone will comment that your phone was off & the tone of voice normally conveys their annoyance at having to contact you at a more conveniant time for you, if I want to turn my phone off i'll damn well turn it off, it's not broken, the batteries not flat, I just don't want to talk right now!!
Hands free kits: Fine in a car, in fact I hope you all use one whilst driving but if you're going to use one of these in public then don't give me evils if I think you're talking to me, all I hear is a voice, I don't know until I face you that you're using a hands free.
Loud conversations: I don't want to know that your uncle screwed your mother out of a mountain of money because it was revealed she had a different father who was your cousin (actually that conversation would be interesting to overhear).
The point is I don't want or need to hear your personal affairs, if you must discuss personal stuff then wait till you get home, make a pot of tea or coffee & discuss it over the phone with your best mate not the people crammed into the bus/train with you.