Katana it's unbreakable though it goes through a long proccess to make it.
I thought the world settled that the katana IS NOT A MEDIEVAL WEAPON! Though, they are pretty sweet.
I'd Probably choose a large battle axe. They totally dominate. To quote Ranger's Apprentice (I don't remember exactly):
"What if I'm attacked with an axe?"
"Shoot him with an arrow"
"I can't, my bowstring's broken, remember?"
"Then run away."
"I can't do that, either, there's a cliff."
"Then, jump off the cliff. It'll be a lot less messier that way."
Also, the axe was used for executions. It would cut off a person's head in one swing. They didn't use swords for that business because they're more useful in quick combat. Yes, I realize that a sword could take down an axe. However, If neither fighter has any form of defense, the axe would win with one hit if it took the first blow.
You have to respect the fact that these were commonly used by vikings. Swords were more expensive. These were cheap, yet useful. When someone thinks of a viking, they connect it with an axe. One could argue that they connect it with a horned helmet, and, as we all know, those were not used in combat.
An axe can also be used as a a tool. If you have an axe and a sword lying around, and you want to chop some firewood, what are you going to pick up? The axe. This goes along with my previous argument, in which I stated that axes had more power. They are more durable. They are better at cutting things up, specifically, harder things.
Hey, you have a knife? Oh, cool, you could have a chance at beating me if I had a sword, but look, I have an axe. So, you can stay here and die, or you can run away, because all you have is a knife, and I won't be able to catch you if I'm carrying a heavy axe.
Comparing the weapons side by side, an axe will win. Comparing weapons in combat is different. Any kind of sword could be superior to an axe. It all depends on the warrior. If you're trained with one weapon, don't pick up another unless you're learning. Got it?
