Exploding targets that are cheap, easy, and safe to make! Shooting these is a lot of fun because they make a loud pop when you hit them.
25 Pack Splatter Targets 12 x 18 Inch Reactive Targets Largest Splatter Effect #RadioactiveReactiveTargets
Reactive targets from mostly recycled materials. This is intended for use with guns, but would be just fine for slingshots, water toys, rubber band shooters, marshmallow shooters, etc. Just use lighter targets (this method uses wood).
Making your own reactive targets over a weekend from things found in storage.