Well there was the classic:
You: Did you watch Spasticsayno last night?
Them: No.
You: HAHAHA... you're a spastic.
Then there was a stupid one in my school:
You: Are you a PLP?
Them: Erm... yes?
You: HAHA you're a Public Leaning Post!
And then you lean on them. Until they inevitably hit you. To be honest I still don't get the point of that one.
Then there was the genious PEN 15 Club:
You: Do you want to be in the Pen 15 Club? All the cool kids are doing it.
Them: Oh, yes please.
You: OK we need to put the special club mark on your forehead...
... at which point you get out a fat permanent marker and scrawl PEN15 on them...