Every group member must find a partner of approximately equal height and weight, if possible.  The partners will lock arms with their backs to one another.  With arms remaining locked at all times, the partners will sit down on the ground, kick their legs out straight, and try to stand back up.  Then groups of four will try the same thing.  Then groups of eight, sixteen, and eventually, the entire group together.  This is the perfect activity to begin a trust sequence.