I admit that I do this every single week:
Me: (brings a pile of books up to the counter at the local Barnes and Noble)
Cashier: Do you have a membership with us?
Me: HAHAHA NO LOSUR*
C: Ooookay. So how will you be paying for these books?
M: PAYING? LOLWUT!?** I WAS JUST GIVING THESE BACK TO YOU SO YOU COULD RESHELVE THEM
C: Oh, I see you have a Nook.
M: AHAHAHAHAHA NO UR A LOSER X 10 THIS IS A KINDLE MAFAKA
C: Sir, I'm going to have to ask you to exit the store.
M: I'M GOING TO HAVE TO ASK YOOOOOU TO EXIT THE STORE
C: (calls security)
M: (runs out, turning at the last minute) AMAZON BITCHES
*actually I do have one and I use it pretty regularly.

**pronounced "lolwut". The emphasis is on the first syllable.