One of my favourite tools at the moment is the Japanese mill-tooth file, which I really prefer to call a rasp, because it has a similar effect – its capable of hogging off a lot of material (or even more effectively, a planing rasp). I like it because it works as though the face of the file is covered with hundreds of tiny plane edges, essentially shearing material off. These files are made by Japanese company Iwasaki, and are considered sculpting tools.
The face of each tooth on the file is formed to allow for a mini chip-breaker. This helps break the shavings off and helps prevent the file from clogging. Here is a close-up of a tooth from the Iwasaki website:
The type of shavings produced depends on the type of wood being filed. I have noticed that harder woods like Ash tend to produce small shavings, whereas softer woods like cherry produce long spiralled shavings.
Supposedly, the files produce a surface equivalent to using 280 grit sandpaper. Below is a piece of ash which has been filed. The surface is extremely smooth. The file works well moving 90° across the grain, or diagonally. They work well in places too tight for a plane can’t get too.
I have one flat file, but will likely get a couple more. Lee Valley carries a bunch of different types, but for more sculpting oriented tools head over to Dieter Schmid Fine Tools, or Highland Woodworking.