Requirements
Objective
Divide a large group into smaller groups.
Description
Each band must have a drummer, guitar player, keyboard player and singer.
Then they mime out their band, complete with air instrumentation.
Then all of the dummers are in one group, all singers in another, etc. You can create as many band members as you need groups. (above example gets you four groups).
Similarly, you can do the same with a baseball (any sports) team.