Dragon Sword/True Dragon Sword/Plasma Saber MKII
The best weapon in the game in terms of overall balance. It's quick, powerful, and has the best combos once all levels are unlocked. It's also the only weapon that gets a bonus upgrade during the story.
The Lunar is a devastating weapon with longer combos than the sword but more strength then the nunchucks or the flails. The best reasons to keep this weapon handy are its charge attack and incredible range. First introduced via the Hurricane Packs, a series of downloadable content for the first game, and was brought back for Ninja Gaiden Black, Ninja Gaiden Sigma, and Ninja Gaiden II.
This non-upgradeable weapon is fast and cool to use, but isn't very practical. On higher difficulties this weapon is a godsend until the more powerful Vigoorian Flails are gained, as this weapon is capable of easily taking out enemy ninja.
 Vigoorian Flails
Bladed nunchuks, these bad boys are fantastically fast and deadly weapons. Capable of ripping enemies to shreds and deflecting shuriken with certain combos, these weapons are both capable of an incredible offense and defense. is found in chapter 10
 War Hammer
This powerful and slow weapon is fun to use, but not as effective as the Dragon Blade as far as speed is concerned. Once you actually obtain this weapon it becomes possible to obtain the Dabilahro shortly after, a much better weapon all around in terms of power, speed, and combo practicality.
The mighty sword is much mightier when fully upgraded. This is a better choice for a heavy attack than the War Hammer. It's power is perfect for taking on slower enemies as well as ripping through hordes of weaker enemies with its Ultimate Technique.
 Wooden Sword/Unlabored Flawlessness
This practice sword can kill foes without decapitating them, but it is limited in moves. You can't even perform the Ultimate Technique. However, it can be upgraded six times. At the final level it becomes the Unlabored Flawlessness, a weapon that as the user becomes weakened, the user becomes stronger. At 10% health remaining, Hayabusa's strength is greatly magnified, and at 5% health remaining he grows even stronger. Capable of taking down bosses in seconds.
This is a powerful slasher, but it comes at a price. If you wield the blade, your health slowly drains, unless the necessary item is equipped to stop it. Only by killing others can you keep this vampiric effect from happening, with moves capable of sucking the life from enemies. In Ninja Gaiden Black and Ninja Gaiden Sigma, the life drain incurred by this weapon is removed and acts like an enhanced version of the Dragon Sword, until it's final upgrade at least.
 Dark Dragon Blade
The Dark Dragon Blade, in terms of moves, is more or less similar to the Dabilahro. In most cases the Dabilahro is the better weapon all around, but the Dark Dragon Blade is still far superior to the War Hammer. It can only be unlocked by obtaining scarabs, thus it only becomes usable near the end of the game.