Being adamantly opposed to using any kind of "weapons" as toys, and this includes water guns, I give my kids plastic squirt bottles, either clean spray bottles of water or even cleaned out plastic ketchup or syrup bottles to squirt each other with.
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My daughter-in-law told me about this one. My family is adamantly against guns and we didn't even feel comfortable letting the kids have squirt guns! So she decided to buy those cheap squirt bottles like you find at the drugstore and Walmart and let her kids use those for squirting water. They love it and it doesn't compromise our values! By cheryl