"I know" = "How dare you suggest that there is information that I am unaware of? I know everything and suggesting otherwise is an unforgivable offense to the natural order of the universe."
"I will" (when in response to the second - or forty second - request to do something around the house) = "I will do it when I'm good and ready to stop texting/talking on the phone/drawing/reading and not before then. And even then I may or may not do it depending on the weather, my mood at the time and if Mars and Venus are in alignment."
"Mom" = "Do not talk to me, look at me, walk next to me or in any other way suggest to the casual onlooker that we might be related in any way shape or form or I will drop dead of mortification on the spot AND IT WILL BE ALL YOUR FAULT."
"MOM!" = "I am about to slay the other products of your womb in the most hideous and gruesome way possible unless you intervene and spare their worthless lives."
"I'm hungry" = "You never buy anything actually edible. Why is all this healthy crap the only thing to eat in the house? I demand you drive me to the nearest junk-food restaurant immediately."
"I dunno" = "I'm not really listening to you but I don't want to listen to your latest version of lecture 2.0 so I'll give you a fake answer to shut you up for the moment."
That is all I have for now but I am quite confident that this list of commonly used teenage phrases will be added onto in the not-too-distant future.
And Mom? Dad? Have I apologized for my teenage years lately? I'm so so sorry!