I'm not sure if this fits here or into a more general thread, but hows about the removal of stickers from catridges (especially the labels) without leaving residue or marks? I've got plenty of second hand items that get price tags added that are a pain to get off.
From regular plastic surfaces a light citric solution (diluted versions of general store 'goo gone' or whatnot) will tend to remove the glue left behind by stickers or tape. This doesn't though help with masking tape which seems to bond much more with the plastic.
Sorry if that doesn't fit or something.