... a photo pencil? It's a pencil that you can mark pictures with and then it will wipe off... It also doesn't dig into the pic like a regular pencil. I searched on here, but didn't come up with anything.
OK, so I found some "grease pencils" (aka: "wax &/or China markers") on Ebay... I'm thinking I'll try one of these. I'm going to try to find one @ Walmart or an office supply store... don't want to pay shipping on a crayon!!!