I have had good luck grinding dental tools with my Dremel into custom scribers and scrapers. One in particular was ground to a sharp 90 degree edge, good for getting crisp inside corners where sandpaper cannot reach.
For larger scale models (I work on 1/96 scale ships) woodworking scrapers can be ground into custom profiles and used for various scraping operations that can replace sanding and give much better results. For example, Burke class destroyers have 10 degree inclined supersructures, so I made a scraper with a matching profile to clean the joint where the superstructure meets the deck.
I also make a lot of custom sanders using both styrene strip and acrylic, gluing on strips of various grits with CA. The nice thing about these is that you can come up with all sorts of handles and extensions to get into small areas.
Ex-acto knife blades can be reground into custom scrapers and smaller knives with caution - wear eye protection and be safe when working with these very sharp objects. Worn out files can also be reground for this use.
Sewing machine needles and pins can be ground into drills much smaller than commericaly available. I have had some success with Etymological mounting pins too.
Just a few tricks!
Kurt