I've got two that are bugging me at the moment: "I know, right?" and "I'm not going to lie, ..." Both phrases drive me up the wall. It's probably because I've mostly heard them used in an arrogant context. Bonus: Internet posts consisting of the single word "This." If you have nothing new to add, why bother posting? Or if you absolutely have to point out your agreement, why not say "I agree with you."?