I was working on the wa handle for my honesuki project yesterday, and decided to slice the handle lengthwise and cut a groove in each half to provide a place for the tang of the blade. The first side was no problem, however I had a small miscalculation on the second half. I now have a nice groove in the side of the middle finger of my left hand.
The good news is that the handle piece was not destroyed so I don't have to start over from scratch!
Moral of the story: power tools are dangerous.