Someone mentioned mine, which is using "good" when you mean "well". I spent the summer with my parents and my mother must've picked up that habit from the other ladies in her retirement community because they all. do. it. and after a summer of:
"How are you?"
"I'm doing good."
"Well."
it's become a pet peeve. I now yell at the telly when someone on there does it. I hear it everywhere! And, seriously, I have no idea why my father is letting my mother get away with such atrocious grammar. People will think no one loved her enough to correct her.