Evolution!This game is fun for groups of just about any size. It can be used as an icebreaker, a field game, and as no cost entertainment requiring no supplies.
Explain that this game is sort of like "rock, paper, scissors" with a twist. Crouching down to the ground, yell "EGG". Standing and strutting like a chicken, yell "CHICKEN". Standing up straight and acting like a dinosaur, I prefer 'Velociraptor' (see Jurassic Park if you need inspiration and are old enough), yell "VELOCIRAPTOR", or you're favorite dinosaur. Now, for the final character I like to go to 'Elvis' and flash some mad hip gyrations, guitar strums, and lip lifts, however, any pop star your group will laugh at works. Yell "ELVIS" and show your moves. Have your group participants mirror each movement/ character as you introduce them.
Everyone starts out an egg. The goal is to "evolve" into Elvis. Eventually most participants will cycle through being Elvis for a short time, however most will be chickens and eggs for a majority of the game. Participants move up the ranks from Egg to Chicken to Velociraptor to Elvis (or whatever fun or even educational levels you wish to create) by playing each other in "rock, paper, scissors". Winners move up a level and losers go done a level or stay an egg. The play is at random and participants wander about playing each other and acting like the character level they are currently ranked (egg, chicken, etc.)
Play generally takes a few minutes to start as participants get used to the game. Play picks up, and I find many groups lose interest within 20 minutes. You can simply end the game or add your own creative twist. I enjoy a good spontaneous dance party with everyone choosing their favorite character from the game to dance as.