This Activity is meant for Boy Scouts.
Decide for yourself if it is appropriate for your younger scouts or not.

candle and squirtgun for each scout (or at least 4 candles and guns)
a lighter
water supply

Position duelists about 10-15 feet apart, depending on the range of squirtguns.
Stand a candle on the ground by each duelist and light it.

On "Ready - Aim - Fire!", each scout shoots at his opponent's candle one time. Repeat until the first to extinguish the candle is the winner.

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You can have a competition within each patrol to determine the patrol champion and then have them represent their patrol in a troop championship.

You can have duel winners advance to determine the troop champion in a single-elimination tournament.

You can have each patrol duel every other patrol once and keep track of overall win-lose record to determine the champion patrol. A different scout in the patrol gets to do each duel so everyone gets a try.