Well, if you're ingenious... They do sell pepper spray in the "riot extinguisher" size, for the corrections market. It looks like a big red fire extinguisher. Plumb one of these through the rocker panel on each side.
It wouldn't get you in as much trouble as the South African anti-carjack propane flamethrower.
I do love the idea, and it wouldn't be hard to build. "Will that be Regular, or Extra Crispy?"
“The police of a State should never be stronger or better armed than the citizenry. An armed citizenry, willing to fight is the foundation of civil freedom.” Heinlein