This is a reaction game good for groups of any size. All it requires is one Huynh Truong giving directions (if a large group, use a microphone and speaker). The HT will call different places the players should place their hands before trying to grab an object on the ground before the player they are against - "head, knees, shoulders, ears, head, eyes, grab!"
For large groups, you can modify the game this way: have teams of equal size go head to head. The player from the losing team from the round is out, and their teammate behind them goes next. The team that is eliminated first loses.