A gentleman named Chris responded to the earlier post about the girl who defended herself by suggesting that pepper spray would also work.
It turns out that Chris sells pepper spray and related products through a website called Defendthyself.com. He blogs on the subject of these weapons and related self defense issues here. I don't agree with him on many issues -- I don't think weapons are your most important line of defense, for example -- but he does have a perspective to offer if you're thinking about buying pepper spray or similar weapons.
I would not give pepper spray or any other weapon to a child for self defense. Some children might get silly and spray their friends. And it wouldn't be hard for a mugger to take the spray away from a child and use it against her or him.
However, for adults pepper spray and similar products can be useful self defense tools IF you know how to use them. These things are just like any other weapons -- useful tools in the right hands.
But just like guns, they can also do you more harm than good if you don't really know how to handle them. And if you're nervous, you might well use them in situations where they aren't required -- something that can get you arrested for assault.
So don't just run out and buy something. Read about the different products and see if they would make sense in your situation. Make sure they're legal in your jurisdiction -- some products aren't. Find out if the seller offers any training course on how to use it. And if you're the nervous type -- the kind of person who might spray an innocent bystander -- take a self defense class or do some other study to learn calmness before you buy any kind of weapon, whether it's pepper spray or a gun.
A weapon is only good for self defense if you know how to use it.
By the way, Chris, if you're reading this, please let me know if you offer any courses on how to use pepper spray and other products. I'll post the information on this blog.