What is good for removing staburn water spots on car windshield?

Try some pure distilled vinegar. That usually will knock them out. If that doesn't cut it, try some polish with a pad and work it in. You can try and mild polish or try SYSTEM ONE X3.

I use a product called Water Spot Remover from Danase.

try some good old plain clear vinegar, put some on a clean rag and gently rub out the spots, I say put this on a rag first then apply to the glass because you don't want it to drip anywhere on the paintwork as it's pretty acidic and it might damage it, the vinegar worked on my car years ago I had stubborn water spot stains and I went out and got the best glass cleaners that the shops had to offer and none of them worked but the good old vinegar did the trick!

i found a really good product you can get at a hardware store or maybe a wal-mart if there is one near you. it is called SPOT-X it is a powder substance that with a sponge and a little water will take about anything off a window from hard water stain to about anything

Bar keepers friend, make a paste with it and polish off the water spots.

Rain-X works for me.

vinegar or diluted muratic acid