Per group: a post and a ball, the posts are preferably (but not absolutely necessary) arranged in a circle or rectangle.
The number of persons per group is less important (but all groups are about the same size).
The first task for the groups is to score 10 goals with a through-ball.
When you have finished with that, the person who scored the last goal runs to the trainer to get the next task. Which group performed all the tasks first?
The trainer has a piece of paper with tasks on him.
When someone comes to get the next task, first ask which task has just been completed (this can vary considerably over time) and then give the next task.