Make a machine by each person acting a different part of it.
Start with one person making a noise and a simple repeatable gesture.
When the person has a rhythm and another person has an idea for a movement which connects to the first gesture that person joins the first person by making a new noise and movement which connects to the original gesture.
Each person joins in with a new noise and gesture and connects to the others in some way until everyone is involved in creating the machine.
Afterwards discuss what the machine was and what each person thought they were doing as part of it.
VARIATION: Decide on a type of machine and then have everyone create it together - everyone starts at the same time.