Multi Purpose Oil Based Primer by Sherwin Williams - water soluble stains can't be blocked with a water based primer. This primer blocks water sensitive stains with one coat. It also blocks grease, ink, and pencil stains. A water based product can be applied on top of it. Works great to: block tough stains like water marks and ink; block strong odors like cigarette smoke; block greasy stains like crayon; seal wood with an open grain.
Make your own Wood Stain -- they put vinegar and a steel scrubby in a glass jar for 24 hours. They loved it on all the woods except pine (it was okay, not great); and think that any old steel objects (nails?) in the jar will work just as well.