A large wall and a tennis ball (or another bouncy-type ball)
To eliminate the other players
Everyone is given a number from 1 to however many kids you have. And, you can also, split these people up into groups, but you don’t have to (ie. Numbers 1 through 5 are team 1, 6 to 10 is team 2, ect.). And, then find a wall with not much on it: no/few basketball nets, no/few posters, ect.
All the campers need to do is throw the ball against the wall (and, you can designate a minimum hight that the ball must get to depending on age) and call out a number while all the other kids run away. Who ever’s number was called must chase the ball. Once they have caught the ball they then must yell “MOUSE!” and everyone must freeze in place, may they be on one foot or maybe sitting on the ground, they can’t move.
If the person who has the ball sees someone move they can call “RAT-TRAP!” and that person is out(You may want to put a time limit on how long they have to call someone). If the person with the ball is content they must then ‘roll’ the ball (as if it were a mouse scurrying) at another person. If the ball hits someone that person is out. If the ball rolls and hits a wall or comes to a stop before it hits a person then the person who called ‘mouse’ is out. Now if the the ball missed then whoever happeneds to be closest to the ball when it hits the wall or stops has a chance to throw it (or they ‘may’ pass it to another player). If the mouse-caller did get someone out (by calling them out or rolling the ball) then they get to throw the ball. Only one person can get out a round.
Once everyone is out. Or only members of one team remain then the game is over. Or you can even start a second game with the people who were eliminated.