I don't know that I have a lot of pet peeves. I kind of agree with
@baymule I expect people to do stupid self-centered things so it's not so much aggravation as pity. I just think "Wow, someone has to live with that person. I'm glad it's not me". I think that helps my blood pressure.
But there are some things that I consider less than thoughtful, friendly, courteous behavior. I see a lot of these are about driving. I haven't seen anyone mention people that don't know how to use an acceleration ramp to enter an interstate or similar road. Instead of using the acceleration ramp to accelerate up to traffic speed and merging with traffic, they don't even think about merging until the lane disappears. Then they either force their way into traffic, whether there is room or not or they stop and wait for long break in traffic. Of course I make exceptions when traffic is so heavy you can't merge but I'm talking about yesterday when an 18-wheeler slowed down and gave them plenty of room, but all they could do was slow down even more. That's dangerous.
Another driving one is people that don't know how to use a 4-way stop. I'm not always sure if that is arrogance or they just don't have a clue about life going on around them.
@sumi I've driven in Ireland, I understand. It's not just the drivers, it's the roads. In its own unique way, Ireland is about the most challenging place I've ever driven. I have been a few places though that I did not drive, the company provided drivers. In Ireland I was on vacation.
I don't like robo-calls because I can't play with them but telemarketers aren't that bad. I've been known to try to get them to buy candy or raffle tickets the kids were selling at school, even if the kids had long ago graduated. Or I may ask them why the "do not call" list doesn't apply to them. With some of them I take my time and try to tie them up as long as I can, maybe getting them to explain why my requests to be on their "contact once a year by mail only" list continue to be ignored. I'm usually not rude to them but I did recently make an exception. When someone said are you aware of a computer problem, I asked if he was aware I thought scam artists like him should be surgically fixed so they could never breed. For some reason he hung up.
I can't think of any interpersonal relationship things that haven't been mentioned so I'll close.