Usually said by lame high school underclassmen who haven't realized that it's not a cool thing to say, and in turn look like complete idiots to anyone who happened to hear them.
Bill: Hey Steve, can I borrow your calculator?
Steve: Oh sure. *attempts to hand Bill his calculator, but accidentally drops it*
Bill: EPIC FAIL!
Steve: Oh sorry, I thought you were cool. No, you can't borrow my calculator.
Jim: And I don't want to be friends with you anymore.