How can I remove permanent marker from a LEGO brick?
I use pure Eucalyptus oil. It works wonderfully. Keep in mind that if you are using it on LEGO, it will also remove the original printing (but won't harm the plastic itself), so I wouldn't recommend it in that case. But other than that Eucalyptus oil can remove marker, paint, glue-residue, and all kinds of gunk much better and faster than products like Goo-Gone. I'm an artist and use it on a regular basis. Eucalyptus oil is available in small bottles at health-food stores, larger bottles at pharmacies (that's what I use), and also at some Asian stores (usually the cheapest).