Insults:

You're a person of rare intelligence. It's rare when you show any.
You're as useful as an ashtray on a motorcycle.
I guess you prove that even god makes mistakes sometimes.
I hear the only place You are ever invited is outside.
You're at least one Brady short of a Bunch.
The wheel is turning but the hamster is definitely dead.
There is no vaccine against stupidity.
I'll hit you so hard you'll have to unzip your pants to say hi!
I used to think that you were a big pain in the neck. Now I have a much lower opinion of you.
I'd like to break the monotony; where's your weakest point?