This game only requires space, and no equipment or prep is necessary. Begin by inviting every person in the group to find a partner and form a two-person cell. Explain that you, as leader, will clap your hands. If you clap you hands three times, players must then quickly adapt and form a cell of three. If you clap your hands four times, the participants must be huddled into a cell of four, etc. Anyone not in a cell of that size is out for that round.
Repeat this procedure, clapping your hands a different number of times to form new cells. Eventually you will get down to three or four people. The game can begin again with another person leading the clapping. This game becomes more fun as people rush to create new cells, and it is also a wonderful way to form teams for other games.