I heard that using a Mr. Clean Magic Eraser works wonderfully for removing marker marks from cartridges. Someone on GameFAQs posted a before picture and an after picture of a Little Samson cartridge that had someone's name on it in permanent marker (not so permanent now is it

?). The thing was perfectly clean. If you want a free Mr. Clean Magic Eraser you can go to their official site (mrclean.com) and click on the link at the bottom left.