Ok, this is probably my favorite thing to call someone I do not like: an Asshat. You can call someone an asshole, and Wikipedia tells us that Asshat is a derivative of the all-encompassing asshole.
Fair enough. But I think asshole is old school, and asshat is the new school. Being that as it may, you may find giggles rather than anger when this word is directed at someone.
They will stop laughing when you call them asshat, and then follow it up with a left hook into their stupid eye.