Well to be honest ours aren't really PC! but we do call each other... Spaz, Mong & Flid! But when I say them I don't mean them as an insult to anyone with a physical or mental disability, to me its just like saying numpty or nutter which we also use! I do tend to be very careful not to use these terms outside!!
I remember years ago at school we used to call each other Joey's after seeing a programme about a Disabled man named Joey Deacon, in fact this man is somewhat remarkable.
http://www.spleen.dsl.pipex.com/jd-history.html