As for me, there's one guy in a few of my classes who's really perpetuating one of my biggest pet peeves -- namely, an idiot trying to look smart. Every time a teacher says anything, he shares how much more he knows about the subject (usually something he just read from a textbook), and his sentences always start with "actually". Example:
Teacher: "King Louis tried to escape from France by dressing as a woman, but someone recognized him and had him taken to the Bastille. That was pretty amazing, since they didn't have TV's or photos back then."
Guy: "Actually, that person had seen Louis's face on a coin."
Teacher: "Yeah, I know. And never use the word "actually" in a sentence, it sounds awful."
If only more teachers reacted that way to him, he'd shut up.