Back in my military school days, my buddy had a fake/neutered grenade on his desk. He used to call the plebes into him room and he would talk to them, while seemingly fiddling with the grenade. He would then "accidentally" release the pin which would go flying accross the room.
The looks on the plebe's faces at that instant were always quite amusing!
You used to be able to buy the neutered ones at the gun show for $5.
Probably some Congressmen/Congresswomen as well.......but not at the gun show, lol.