My vote for the cabinet scraper as the most under-rated tool in my arsenal. Sanding, no matter what kind of sander, is always a bit of a drag but using a cabinet scraper as one step in the finishing process not only saves on the amount of sanding but totally eliminates any machine markings with ease. When I have the opportunity to build a more traditional piece of furniture I always rely on my cabinet scraper and never use any power sanding equipment.
As a footnote, I noticed that Lee Valley has introduced a replacement blade for the old Stanley Cabinet Scraper. I probably will order a couple just to have them on hand. I didn't realize that these blades are getting a hard to find.
Best regards,
John