The toothpaste that the dentist has
Most people think that you can't buy the same kind of toothpaste as the dentist because they use special equipment. It's actually because it's highly corrosive, and that's why you're only supposed to have it in your mouth when the dentist does it. It really cleans your teeth, but if you used it every day, it could melt your face. That happened to this guy my cousin knows. He stole some from the dentist, because he liked how clean his teeth felt every time he went. He ended up having to have a robotic jaw installed.