Pepper spray is the most popular self defense product in the world. Law enforcement and military units the world over use pepper spray for law enforcement and crowd control. The main appeal to the civilian community is its' effectiveness and quite frankly the fact that it is cheap.
On the negative side pepper spray isn't always easy to find. Wal-Mart used to carry it but no more. I found a police supply store here that had 2 or 3 to choose from-not too good a selection.
Pepper sprays are not legal in some states. Check with your local police department first before you get one. You don't want to get in trouble with the law.
Pepper as a weapon has a long history going back thousands of years when Chinese fighters would gather pepper and other hot spices to throw at their enemies.
If you want something that really works pepper spray may be just the thing. It causes the attacker to gasp for air and induces temporary blindness. The eyes can actually shut down. Coughing and choking are common. It is very nasty stuff.
Pepper spray effects last as long as 30-45 minutes against humans. It is very effective against dogs, bears, coyotes and mountain lions or any animal with a sensitive nose. Almost all postal carriers have pepper spray.
One of the unique qualities of pepper spray is because of its' nature it can be disguised. One looks just like a lipstick container, one is packaged in a container that looks like a pager, another as a ring. But you won't find those in any store.
If you order on line you will find a much better selection, very competitive prices often with discounts available, different shipping options, and no sales tax (yet). You just can't match that in any retail store. Most websites have 40 to 50 models and sizes to choose from.
Once you decide where to get one and which is best for your situation, do your self a favor and try it out (outside of course) and practice using it so when the time comes to use it will feel comfortable to you. And know that wind and rain can change the direction of your aim.
Most pepper sprays work in a range of 6-12 feet. There is pepper spray gel that works up to 18 feet and a Pepper Gun has a range of 25 feet. They use a fine grain stream. Foam and fogger products are available also.