I accidentally discover that acne soap will take hard water spots right off. Just be careful to not get it on plastics and rubber because it might dry it out. I had the stuff below
http://www.neutrogena.com/econsumer...&target=/products/face/oil-free-acne-wash.jsp
http://www.neutrogena.com/econsumer...&target=/products/face/oil-free-acne-wash.jsp