I’ve also heard people use them to break car windows. Same principle as a glass breaker, but you can hide it more easily, and if the cops find it you can always lie that you’re going to a shop to buy a replacement.

That’s it. I have a friend that worked in a bike shop, they called it a ‘Crack Attack’. His shop specialized in airhead BMW repairs, the spark plugs are easily accessible on those. Usually some of the cooling fins ended up broken.