Well, I'm not much of a "potty mouth" but here are my favorite insults...

~Waste of human flesh

~Oxygen Thief

~Posterchild for Retroactive abortion

~You weren't hit with the ugly stick, you fell through the whole ugly tree

~Asking too much of your deodorant

~God made Oklahoma so even people from Idaho would have someone to make fun of

~Rip Van Winkle didn't get as much Beauty Sleep at you'd need

~You'd ugly a blindman to death

~Were you born and idiot, or is this just a midlife career change?

There's enough to get you started ;~D

My favorite insult recently came from Brad:

"Do you swallow your tongue if you aren't concentrating on not doing so?"

I also adopted the term "asshat" from JU.

Umm...I don't think you want me to whip out my swear words.  The thing is, I can get very creative with mixing and matching...and while funny and insulting at the same time, may destroy the fragility of your innocence.

~Zoo

Hard to top that one!

How about "South end of a north bound mule."