Every morning I play a team building game with my third graders. It is always a short game (between 5 and 10 minutes). It always involves cooperation. Today we played the most fun game I've played with them.
Here is how the game works:
One student goes out in the hallway, while I and my class set up a task for them. We did things like writing on a whiteboard, pretending to read a book, and pressing play on a cd player. The student from the hall comes back in the room and the whole class hums. They hum louder as the student gets closer to accomplishing the task. They hum more quietly if the student gets farther from the task at hand.
It was so much fun--even for me. It was also a great team builder because it is really an example of the whole class thinking with one mind. I highly recommend this game.