To that end, I present for you, The Shakespearean Insulter. What better way to insult your friends without them knowing they've been insulted (unless they are literary snobs).
Here are a few:
You are a shallow cowardly hind, and you lie.Classics, I tell ya.
[Thou art] not so big as a round little worm.
Thou wimpled pox-marked bugbear!
Thou rank ill-nurtured giglet!
Methink'st thou art a general offence and every man should beat thee.