DO NOT use the sharp end of the axe as it will stick in whatever it hits -- fine if you just made a perfect strike on a solitary bad guy that instantly dispatches him to Allah.
Not so good if you get it stuck elsewhere and you have to wrench it out while bad guy #2 is doing a number on you or others.
Serious neurological damage will be inflicted with one good whack on the head from the blunt end and does not require anywhere the same degree of skill as using the sharp end -- don't use the sharp end unless you've recently done a couple cords of wood.