There are too many things to list that grind my gears nowadays, but it basically comes down to one or two things which really tip me over the edge. All the issues are caused by people that either don't keep themselves "in check" or that don't have others around them to help with it.
If you don't keep yourself aware that the things you do, or how you act as a person, can cause many other people problems, then you believe that everything you do is the right way, or only way.
Having good people around in your life, that you will actually listen to, helps greatly with this. It really all comes down to how open or closed minded you are.
Driving, a source of constant frustration to many nowadays, is area where learning something must be frowned upon by those that can't be told the correct use of the Highway Code. I know people that believe it's "only a guide" how to do things, and that no actual laws are contained within!
I had a local second-hand shop that stocked everything, mainly from old house clearances. His prices were the most ridiculous I've ever seen. The reason for this? Well, he wasn't aware of the online world and auction site prices. He was told many times that pristine items were selling for much less than the dinged and rusty items he had. A shame he's no longer in business but his blinkers certainly stopped me from offering money for the many old razors, bowls, bottles, etc that lined his shelves. He was so out of touch, and didn't want to broaden his knowledge, that he lost quite a bit of money when he closed.
I come across examples of this mindset on an almost daily basis and it only helps me to maintain an open mind and not accept that I know everything I need to know in life already. I have a smaller circle of friends nowadays as I don't need pretentiousness, ignorance, etc, in my life. I'm not going to become the person that says "this soap is the only one to use, it's the best", or "the Fusion is the only razor to use". I'm not going to be the one standing in the middle of a street shouting that everyone else is wrong for not believing what I do. I think we'd all get along better if most of us took our blinkers off and took the time to think about what we do and the effect it had on those around us. Just because someone is doing something different doesn't necessarily make you right or them wrong.
Gears unground!