Create thin, even walls for intricate carvings. This simple tool hogs out tons of material and creates a smooth and even interior. Gouge horizontally to remove the bulk, then scrape vertically to smooth the interior.

Fun backstory: The original prototypes I made for this were fashioned from steel and aluminum flat bar (back before 3D printing was as ubiquitous as it is today) the 3D versions work just as well and feel safer to use. Fun to see the progression. 

Happy Halloween!