One thing that I really can not stand is the phrase "you know" when describing something. It's as bad as "like," "um," and "uh," when it comes to filler. Something involuntary to cause a pause when your brain can't quite put the right words in order in conversation.
Whenever a customer (or even someone closer actually conversing) injects "you know" into their sentence when going into detail on something to better help me understand, my immediate thought is, "No, I don't know, that's why you're telling me."
I'm not perfect either, but it's a habit I've broken pretty well. I've even winced when I said it recently.
I just need a super-villain weapon that changes the brain waves of everyone across the world to be more precise with their language!