As far as a shootout goes it would be difficult to make it look as real as this chase does. Most fake guns look too fake. I did have a friend that bought a 1911 BB gun and either cut the orange tip off or painted it black. It didn't look bad and I think he paid around $20 for it.

If only it was possible for you to do that handbrake turn where the car turns all the way around and you start driving backwards like in a couple scenes in the Fast and Furious movies. A large parking lot and a small car might make it possible although I've never tried such a thing.