For me, I have serious issues with "OK" lol.
Now don't get me wrong, if I get a reply of "Ok, that sounds good" or an occasional "OK" as the sole answer, I twitch slightly but its not a big deal.
But when holding a conversation, especially in a text only conversation, and get more than one "OK" answer in a row, it makes me want to explode, and gets me angry. Even worse, when there is a Yes/No response warranted, and "OK" is what I get lol.
This really tripped me out, and I couldn't figure out for a long time why it caused such frustration/anger on my part, until I realized that I'm craving information, that is the reason for holding the conversation, and it feels like I'm being starved of the information I need to function.
My poor wife in particular, she has pain in her hands semi-regularly, and when typing it often times becomes easiest for her to use the easily typed "OK" rather than something else longer (but containing more information). I try so hard to let it roll off, and she knows that it irritates me, and tries normally not to use it too often, but man its tough sometimes. At least we've worked out that when I start getting frustrated b/c of this, I kid around usually asking if she's from OK-lahoma, and she usually gets the hint that i'm getting frustrated, and we both get a chuckle and it diffuses things usually pretty well.
Seriously though it trips me out how much it bothers me, and I feel rather childish at times having such issues with it, but its just one of my many quirks I guess heh, just trying to get better at handling the situations as they arise instead of blowing my top.