Misuse of the word "irony", particularly when what the user means is coincidence.
The American use of the affectation, ", no?" especially in today's chat environments. Sure, the French do it and it is part of their culture. When Americans use that expression it just sounds arrogant and wrong to me.
I don't raise a big fuss about either of these because, like the way Shawn rolls toothpaste tubes, it doesn't bother me enough to really go to the trouble of mentioning it. However, I mention it today in order to get it off of my chest. What are your linguistic pet peeves?