Honestly, most of these lines are absolutely terrible. You don't want to start a fight with the guy (well, maybe you do, but that's for another topic). You want to show that you are 100% confident and will not be thrown off your game by 3rd grade insults.
If you say something incendiary like "It was good enough for your mom", the guy is most likely just gonna stand there and throw more insults back at you, or punch you in the face. This accomplishes nothing. Ideally, you want the guy to realize he is not making an impact on you and leave as quickly as possible.
My first suggestion would be to ignore him completely and keep talking to the girl. People are only ignored when they are weak or their comments are inconsequential. There's a chance he will just walk away right there.
If he doesn't walk away, he'll probably repeat himself or say something else. Calmy pause, glance over at him, and say "That's a good one, bro" and pat him on the shoulder. Then immediately go back to talking to the girl, like he isn't even there.
You don't want to treat an AMOG like an enemy (as most posters here suggest), because that will only make you look immature, insecure, or get you involved in a fight. You want to treat the AMOG like he's your annoying little brother, or that kid from high school who always tried to hang out with the popular kids but was really a loser. Treat him like a nuisance, so trivial that you can't even be bothered by anything he says or does.