Delivered in a Quiet disarming voice, I see that you have been educated beyond your intelligence.
Then there's the time I'm sorting through my wallet, looking for a receipt when a coworker picks up a piece of paper and asks "whats this 900 number for?" Picking up the same blank piece of paper, "This one, it's for your sister".
...two, actually...both from films (I don't know if they're particularly good insults, but they've stayed with me):
...Man, the only way you're gonna get a piece of pussy is if the bitch dies and wills it to you; and then, maybe.
...I've also been partial to, "I wouldn't fuck her with YOUR dick."