Here's a game I'm using this week with my Middle 1st & 3rd graders:
Have one kid come up to the front of the class and face the board (away from everyone else). Have everyone else stand up.
Ask the kid a question where they have to make a choice. For example - Coke or Pepsi, Soccer or Basketball, Cell phone or internet, Twilight or Harry Potter.
The kids that agree with your player stay standing, everyone else sits down. At the end you end up with just a few kids standing. If you're lucky you can get down to just one. If you wipe out everyone still standing have the last group stand up again and keep going. When you want to end or get to one kid left turn your player around and introduce him/her to their new best friend.
If you have problems coming up with questions or want to make it more interactive have the students think of questions for the player.
The time for this game varies a lot, I've had rounds last anywhere from a few minutes to about 10. It doesn't take a whole period, but I'm getting the kids in their new seats and all for the first part of class.