Guns work good. Having one in my car enables me to drive through the bad part of town late at night and give a friendly wave to the drug dealers and pimps that stand in the middle of the street as I pass on through.
Unfortunately, in California, if you carry a gun in the cabin of your car, the ammo must be in the trunk, or the other way around. Not very useful in an emergency.
Of course law enforcement officers and criminals are exempted from this rule.