What's a "sore thumb" for you?

You know: something that sticks out to you in a bad, unignorable way -- like a "sore thumb" -- every time you see/hear it.

Maybe its apostrophe misuse, maybe it's using cliches like they're going out of style, maybe it's b  a d k e  r n i  n g, or a lack of parallelism perhaps bothers you.

Whatever it is (and it doesn't have to be writing related), let us know. Also, most importantly, why do you think it has such a profound effect on you?