Possibly the greatest comeback ever devised. Although it seems childish it was originally used to almost parody the usual immature responses in mature arguements with immature people.
It was brought to popular use from the popular Machinima, Masterchief Sucks At Halo 3/Arby and the Chief
Matt: Why dont you just stop being such a little kid?
Tom: Why dont you just die?
Matt: No you