Leaving a gun in your car is irresponsible; that's a very common way for them to get stolen.

The modern thinking on this is that you should carry it on your person at all times or leave it at home (e.g. if you're going to a place you can't carry it). Additionally, frequent "administrative handling" of your gun (like unholstering it in your car and re-holstering it when you get out) needlessly increases your chances of a negligent discharge, so moving it off of your body when you get in your car is also discouraged.

Of course this doesn't mean that everyone knows/thinks this way (and many don't), but from my discussions with other firearm advocates, this is the modern school of thought.

So—to answer your question—a Glock 19, and yes, as it's on me already ;-)

People who carry a firearm on their person daily are a tiny minority overall - but they're vastly outnumbered in my experience by people who keep a pistol in their vehicle.

I don't advocate for off-body carry in general, but I'd expect it to be far more likely than you might think for there to be a handgun available to someone in a car.

... and yes, as the GP mentioned, firing it in that closed space would suck. It's going to take multiple rounds to weaken safety glass enough to get through it, and it's going to be loud. As a heuristic, I'd say you should assume that if you have to do that, you're trading your hearing for the rest of your life.

Firing a handgun inside a vehicle, even with both ear plugs and electronic muffs, is enough to make your ears ring.

Yeah, I just mean "the gun I have on my waist", not a special car gun. And especially for the police in Texas at the ranch, they would almost certainly be armed, and I'd assume ranch staff would also have access to firearms within some period of time less than total flooding/drowning of car.