About 10 years ago, I had something on a key-chain for self-defense.... I remember now, not the exact name of the object but what it looked like, a kind of built up hollow object that might be best described as looking like a stake. I still have it. I guess it could serve it's purpose. I know there are a number of these self-defense types of objects. They say they can work.
Believe it or not, I think some of these types of objects have their origins from being used by, Ninjas. No joke, look at that kitty-keychain.