When I was really young, for "show and tell" I brought in things like a dummy grenade and a muskett.
Later in high school (late 80's) I presented "What to do when the Heimlich Maneuve fails" - it invloved a steak knife, fake blood, booze, Bic pen and a friend with a sense of humor.
Since I went to Frankford High in Philly, my next presentation was "Her Water Broke, What Now!?"
For the record the kid is a cr@ppy artist no matter how you rotate that picture...
When my junior high social studies class was doing a segment on World War II, somebody brought in a vintage round of ammo. It was a bullet maybe an inch in diameter (you can see I’m not much of a war gun maven, sorry) still in its metal cartridge. The girl who brought it it said she didn’t know if it was live or not. I wondered what would happen if somebody dropped it rear down to the tile floor from about head height, envisioning a loud bang and the bullet going through the ceiling. (No I did not actually TRY that.)