Originally Posted by RedneckFur
Pepper spray is cheap, and easy to find. Every gun owner should have a can for situations just like this. I keep a big can of it handy, and should I ever run into a situation like this, the robber will get sprayed.
Absolutely. It's one place to start when his passive resistance negates the threat of your firearm. Depending on his position inside the car, you might spray some about his head & shoulders to see what kind of reaction that gets. If that's not possible due to body position, soaking the crotch area or the rear-end of his pants will probably take his mind off the theft business in less than 60 seconds.
And, as Dwight55 said, you could make a few $$ renting him your garden hose afterwards.
But like anything else, have some idea of a backup plan in case it turns out that he's not bothered by pepper spray.