In case you are assaulted, it is good to have the means to administer first aid to yourself or a passenger. Having a blowout kit ( a kit specifically for treating gun and knife wounds) is also a very good idea.
Here is a little personal story about the importance of having a blowout kit in your car.
One day Tracye and I were at the park and I had a brand new knife that I was working with, learning how to deploy it and close it up with one hand. Well, in the process of practicing, I closed the knife on my right index finger and sliced it pretty bad. Luckily enough, I had a first aid / blow out kit in the car and I was able to administer first aid to myself and stop the bleeding. From lessons past, I have also keep multiple bottles of super glue in my blow out kit as well. These are great and have come in handy many times. If you like to collect and work with knives, you will eventually get cut. Super glue is basically what the hospitals use to close up cuts like this.
http://www.informationclearinghouse.info/article45274.htm