People saying "literally" way too often and unnecessarily
To clarify, I am not talking about people using literally improperly (though that annoys me too), I am talking about people who use literally to intensify statements in a way that isn't wrong, but is completely unnecessary.
For example, if you say "I literally just finished," the literally is not adding anything; if you just say "I just finished," your point has been made. People go around saying they "literally just got in the shower" or "this outfit is literally so cute," among others, and technically, they aren't wrong, but you can't figuratively get in the shower; the word literally is adding nothing to that sentence, it does not need to be there! As for the "literally cute outfit," what does that even mean?
This annoys me far more than people using literally incorrectly, because this is far more common! I hear this all the time, but I don't hear people say they "literally died" while standing in front of me, very much alive, very often. That one's a non-issue because it's infrequent in my circle, but using it as an intensifier does, and it drives me crazy every time!