I've tried rubbing alcohol, which can work, eventually. Windex is right out. I saw a video of a kid using those Mr. Clean Magic Eraser things, but am not about to rub that crap over my windshield—not with my luck!
I was picking up something else at AutoZone and grabbed this Invisible Glass stuff on a whim. Turns out, it cleans glass better than anything I've ever seen before. I have never, ever seen glass clean up so quickly as managed with this stuff.
So I thought I'd share, while asking if there are other products that also work very well on auto glass. Scotty has recommended Lithium products, but I'm not sure they have anything for glass.
Try the old standby, vinegar and newspaper. It's been working since the automobile was invented.
Of course the problem these days can be finding a newspaper! 😎
The problem today is finding a newspaper you can believe!!!