The skull is very hard. It is very close to concrete in terms of hardness. This is why a lot of people break their hands in fights because they end up punching people in the top of the head with all their might and break their hand and or wrist. Smashing someones face with your forehead is not a bad idea. Just aim for the face because its soft and gives under pressure.
Yeah, bridge of the nose is the spot to aim for.
*stabs the brain with the nose bone*[/Prodigy]
Its an illegal move in combat sports. That should tell you something.