Probably my biggest one is when people inappropriately use the word "rare" to describe a game. You see this a lot of Ebay with people posting Mario/Duck Hunt and calling it rare in the description and/or title, but it bothers me the most when someone says it in person for a game that is not genuinely rare. Or when people say something is rare, but actually it is just valuable like Super Smash Bros or Zelda Majoras Mask. Makes me grit my teeth every time.