This has been a huge help in my classroom with keeping students quiet. They live on my whiteboard.
Print, laminate and cut up.
You can certainly make your own rules and variations but this is how we play in my classroom:
Deal each student a card at their table face up.
If they talk they must turn over their card and they are "out".
Students who stay in for the whole game get a prize (star, marble, etc).
Students are allowed to "Shh" other students.
Set small and achievable time limits for starters while students build their stamina.
I have included bright colours to make them easy to find when you need to collect them.