Your capablity to thoroughly embed your cranium within your own rectal cavity leaves me in a constant state of utter amazement and disbelieve.

Translation - I can't believe how far you have your head up your own ass.

Come up with your own.  

I'd be less apathetic if I weren't so lethargic.

A buddy of mine said this once to another guy we knew that like to use big words he didn't know the meaning of...

Your logorrhea and sciolism are palpable yet rarely germane.

Methink'st thou art a general offence and every man should beat thee.

This dinner is rather shallow and pedantic.

Thine face is not worth sunburning.

(well, these aren't my own, but shakespearean insults are great nonetheless)

It would be much appreciated if you'd rest your jaw and bonded your regenerative organs with a the rear of a small horse.

Translation: Shut up and go fuck a donkey.

Heh, may as well bring this up: http://www.pangloss.com/seidel/shake_rule.html

It's a "Shakespeare Insult Kit"

You take on word from each successive column, and you get your insult!

Here are some examples right off the bat:

Thou rank, coddle-deep codpiece!
Thou warped, tickle-brained malt-worm!
Thou goatish, fly-bittened whey-face!

Let me assure you, good sir, that I could not possibly overestimate your intelligence.