Classic, very simple, elimination, party game. Certainly familiar to many in the United Kingdom. Probably much more fun for younger children and encourages them to pay attention to an external stimulus or change in their environment.
Have some music playing which players move or dance around to. Every now and then music is stopped/paused. As soon as they hear the music stop players have to sit down on the floor. The last person to sit down is out. The game carries on again until only one (or a couple) winning player is left.
This can also be played without music, where players sit down to a given signal such as a verbal command or blow of a whistle.