1. If you're straight, announce that you're coming out of the closet. If at all possible, do so when your grandpa is saying grace. Once the discussion moves elsewhere, quietly start piercing your nipples.
2. If you're gay and your parents disapprove, announce that you're going to be straight all day long as a present to your family. Then say that you need to be excused early because you've "got to go find some (pussy/dick) before midnight".
3. If you're a girl, announce that you're pregnant (again, during grace if possible). Later, excuse yourself and go to the restroom, then come back after a half-hour and announce that you just had a miscarriage so never mind.
4. Flirt with grandma.
5. Forcefully pick your nose. When confronted, explain to them that you'd rather eat boogers than that shit laid out on the table. Bonus points if you start bleeding.
6. Fake neck tattoo of a bulldog with an enormous erection.
7. Play footsie with everyone within leg's length.
8. Wear your iPod for the entirety of the evening. Sing along occasionally
9. Repeatedly and aggressively deny the Holocaust (unless your parents agree with such, in which case, uh, find a new family).
10. If you're a guy-- you know the scene in American Pie where the kid and the pie and the... yeah. Ask if you can help in the kitchen and do that to every dish you can get your hands on. When you're caught fucking the green bean casserole and they find holes in everything else: "What's the big deal? It's not like I'm coming in anything."
11. Hog all the stuffing.