Yoru

Known to be the strongest Sword in the world, the Kokutō Yoru is one of the 12 Saijō Ō Wazamono Grade Swords, under the ownership of Juracule Mihawk. It is an ornately decorated and very long blade with a length of at least 6 feet, as it is seen to be taller than Mihawk himself when it is placed on his back. On the hilt of this blade is a crossguard, though the bars between the blade and the hilt are much longer than average. The blade itself is pitch black with a very strong sheen, and its shape is similar to the German "Großes Messer", a single-edged long sword with a slight curve at the end of the blade.

Abilities
"Without subtlety, a sword is but an iron bar." Mixed with Mihawk's abilities, Kokutō Yoru has tremendous power, as it was seen destroying Don Krieg's flagship with a single strike. While Kokutō Yoru is the sharpest blade in the world, it is also gentle. This was as demonstrated when Mihawk deflected the course of bullets that were aimed at him with only a slight touch of the sword. He can also launch a massive slashing attack of compressed air or energy wave that can reach at an extremely long distance.

Anime and Manga differences
In the anime and video games, the sword's blade is quite thick while in the manga it's very thin.

Trivia

 * For the 4Kids dub, the sword's cross-shaped guard was shortened because it looked so much like a crucifix.