The one that I havn't licked yet is how to
remove crayon price marking
from a paper diskette label or a book page without it smearing or bleeding
into the paper.
Grease Pencil (the paper-bound kind you unwrap) comes off of glossy
cartridge labels and cartridges themselves quite happily with just
alcohol. However, I'm not sure about actual crayons... especially on
porous paper.
Perhaps it'd be a great boost to the Collecting Community to do a
methodical study of the removal of various types of price markings on
various kinds of surfaces. If I ever had time...