Get in a circle. Someone will loudly suggest an activity for the group to mime. Everyone simultaneously yells: "Yes, lets" and starts the activity. Once the activity has been mimed for a while another one is yelled out and the group responds with, "Yes, lets" and starts the activity. For example, if someone calls out, "Lets all dig holes". The group responds with, "Yes lets all dig holes", and every manner of hole digging begins.
Cooperation. Creativity. Confidence building.