We played Army and used cherry bombs as hand grenades....
Ever put dry ice in a glass jar, add water, screw the lid on and then run like hell??? We did...
And then of course there was the "Bangsite Cannon" toy / weapon.
The best was duct taping about ten soup cans together with top and bottom cut out of all but the bottom of the last one. Punch a hole in the bottom with a nail. Ram a tennis ball or potato down the barrel about half way down. Squirt lighter fluid into the hole and shake it all around to become vapors. Then point at your friends about 100' away and see who can dodge the missile!
I am surprized I survived childhood.
How about bottle rockets, launched from a wiffle bat, at each other.. Yeah, that dump.