We had a fad of kids bringing in bags full of those small red dynamite style bangers they'd bought back from ski trips and the like.
Basically anything we could get our hands on was blown up from toilets, fruit, backpacks, shoes, lockers etc etc.
Also remember taking a full replica fully auto ak47 bb gun for some demonstration in English class. Few other kids did the same and we spent lunch time having bb wars in the one building before getting caught by teachers and simply told to stop and clean up.
Nowadays I'm sure they'd have the bomb squad and the SAS swinging in through the windows.
One of the stupider ones was forcing yourself to faint. Crouch down and then stand up and blow hard on your thumb. Dread to think how many braincells were lost
All good fun until one kid didn't wake up for 5 minutes. I think he did eventually after a line of about 10 kids queuing up to try and slap him awake like that scene in airplane.
Triangle monostrap backpacks was another, I'm sure that's why I've got one terrible shoulder/neck.