Kilz 2 Latex Stainblocking Primer
Kilz produces a wide variety of specialty primers. Like Zinsser, some of their primers are shellac based, providing the same stain hiding capability. This one is a latex primer, which has been created to provide the same advantages as a shellac primer, with the convenience of water cleanup. While I cant say that it quite matches shellac for difficult stains, it still does an excellent job in most cases. Although latex based, it can be top-coated with either latex or oil-based paints.