Good insult.

[Amiga500]

Some classics from school...

Your Mum's so old she farts dust....

Your house is so dusty the mice go around in speedboats...

Your Mum's t**t's are so square that the milk comes out in cartons...

[oracleslave]

One for CT.

If ignorance were a disability you'd get the full pension.

[minestrone]

"telll you mum to stop changing her lipstick shade, my cock is like a rainbow"

[thunderlizard]

yo mamma so fat, when she walk across the room she have to make two trips.

[Drewster]

As most of us on CUK are highly intelligent and erudite with rapier like wit I find the classic insults tend to go down well:

eg - You are a Twunt!

[BlackenedBiker]

Yo mammas so big when she jumps in the swimming pool all the water jumps out

Let's get off Mammas.....I just got off yours

[thunderlizard]

Yo momma so fat she got my momma orbiting around her.

[NotAllThere]

There was a lovely abusive rant in a physics usenet forum, that contained something along the lines of

"I'm embarrassed to be the same species as you".

[cojak]

He's dark and handsome. When it's dark, he's handsome

[cojak]

but this is one of my favourites...

I hear what you're saying but I just don't care.