One good way to break apart the group dynamics is to throw everyone out of their element. You can embarrass everyone. Last year I had them eat a doughnut....that was hanging from a rope....and they couldn't use their hands.... Boy, were the pictures great for that game! This year, I'm going to have this game!
Person #1 [wearing plaque that says "The Headless Horseman"]: Hi!
Person #2: Oh, hey! How's it going! You're head feeling any better? Oh... sorry. Forgot...sore subject *cough cough*
What I like best about this game is this: people don't have to be themselves! When other people interact with them, they are speaking to character. Hopefully this gets rid of some of the awkward tension that may pass when you are being introduced to someone new because you'll feel more comfortable interacting with a familiar character. (Does that make sense? I hope it does.)
Once the person wearing the plaque starts figuring out what they are, they can start talking as if they were that person! When the time's up, everyone gets to make a gander at who they are. If you get it right, they get a prize! And hopefully they also made some friends. Like all icebreakers, this can backfire, but it's up to you as the host to get everyone talking and try to mix the groups up a bit.
Weeeee! This is going to be so much fun! :D More party stuff coming up in a bit!