Mine is petty lol, but if a person is smacking or snoring next to me really loud, I tend to get pretty angry or annoyed real fast. Also screaming kids out in public, especially when their parents is standing right there not doing anything to quiet the little...never mind. Let me stop!
It depends who it is.
Some people never get on my nerves at all; they're pure joy to be around and bring nothing but happiness. There are about five people like that in the world.
Others merely have to exist in the same universe as me. There are several billion people like that in the world.