Katana

The Katana (sometimes also incorrectly called the Hayabusa sword) is a special armor permutation unlockable by earning every achievement  (1000 gamerscore in Halo 3 out of 1000, which Halo 3 has 49 Achievements in total.) and all skulls (including silver skulls). The sword closely resembles Ryu Hayabusa's Dragon Sword, and is not usable by the player.

Characteristics
The Katana consists of a normal Hayabusa body armor with a Katana sword affixed to the back with a silver attachment, possibly magnetized. The sheath of the katana is grey and the handle is a reddish brown color.

Trivia

 * There also seems to be some markings on the handle of the sword, some characters looking Japanese.
 * The Katana resembles the first Dragon Sword Ryu gets in Ninja Gaiden, not the True Dragon Sword. Truthfully said, almost every Katana looks similar to those of the Halo version.
 * The Katana armor, like Hayabusa armor, is either scorned or praised by the Xbox LIVE community. The Katana armor is often stated to be just a showcase achievement, having absolutely nothing to do with Halo 3 or the universe itself whatsoever.
 * The Katana and the Security armor permutations both come with getting all 1000G in Halo 3. Because of this, some fans thought that the Katana should have gone with the Security armor instead of the Hayabusa.
 * It is considered by some to be the hardest armor to unlock,along with the Security helm, because of the difficulty of some of the games achievements.
 * The Katana can be stuck with a grenade.
 * The sword counts as an extra part of your body thus making a slightly larger target.