This is just like “Paper, Rock, Scissors”, except the kids will act out the “gorilla” (both hands in the air and a big growl), man (arms folded with one hand on the side of the chin/jaw with a sophisticated look), gun (however you choose to model holding a gun).
Once each child in the group has a partner, have them get back to back and teach them the rules in song form:
“The gorilla beats the man, and the man beats the gun. The gun beats the gorilla, if you tie you die.” and then count all together “1, 2, 3!”
That’s when each back to back partners turns around as a “gorilla, man, or a gun”. Then match up the winners and repeat until you get the final group and have a prize for the winner.
This works better when you play it throughout the week at big camp gatherings and the kids really anticipate playing it each time.