Boy,
Homeland Security's GOT to be going "WTS?", on this one.
What practical purpose would this serve?
Are you talking penetrate the windshield ONLY, or penetrate AND hit a target behind the glass?
As to penetrating the glass, AND hitting a target behind it, IMO(Especially in a "cold shot" situation) forget it. This is a deflection heuristics/conundrum which baffles the world's best SWAT snipers.
As to merely penetrating the windshield glass, depending on vehicle speed, windshield angle(Pickups are much shallower than sports cars, generally, for example.) angle of your position, and other variables; it's arguable that almost any caliber in the right circumstances COULD penetrate the windshield. I personally would not trust most pistol rounds, possibly magnums excepted, to succeed in any general situation.
Also, if you DO penetrate on the first shot, that doesn't mean the next shot's going to be clear. The windshield may not shatter, and still provide protection from following rounds.