Researchers at the University of Pisa, Italy, have solved a longstanding mystery around the honeycombed skull of one of the Italian martyrs beheaded by 15th century Ottoman Turk invaders when they refused to give up their Christian faith.
If you're going to get a hole drilled into your skull, you don't want to use just any tool. (Though most of us would avoid the skull-drilling in the first place.) One researcher used four different instruments on a single skull to compare Neolithic trepanation methods.
You might think you need an extra hole in your head like... well, a hole in your head. But trepanation has been hailed as the "oldest surgery."