In the world of One Piece, there are several powerful and significant swords, each with unique attributes and history. Determining the "best" sword can be subjective and dependent on factors such as the wielder, context, and personal preferences. However, here are a few notable swords in One Piece:

1. Shusui: Shusui is one of the 21 Great Grade swords and a famous blade within the world of One Piece. It was previously wielded by the legendary samurai Ryuma and is now in the possession of Roronoa Zoro. Shusui has incredible cutting power and is renowned for its strength and durability.
2. Yoru: Yoru is the sword wielded by Dracule Mihawk, one of the strongest characters in the series and the world's greatest swordsman. It is an enormous black-bladed sword that showcases immense power and precision.
3. Enma: Enma is a legendary sword introduced in the Wano Country arc. It was previously wielded by Kozuki Oden, a renowned samurai. Enma possesses the ability to absorb and channel the wielder's Haki, making it an incredibly formidable weapon.
4. Sandai Kitetsu: Sandai Kitetsu is one of the cursed blades in One Piece, known for its exceptional sharpness and strength. It has a reputation for bringing misfortune to its owners but is currently wielded by Roronoa Zoro.
5. Mera Mera no Mi Saber: This sword, created by the Devil Fruit power of the Mera Mera no Mi, possesses the element of fire. It was formerly wielded by Portgas D. Ace, the adopted brother of Monkey D. Luffy.

These are just a few examples of notable swords in One Piece, but the series features numerous other swords with their own unique abilities and histories. The "best" sword can vary depending on various factors, including the wielder's skill, the sword's attributes, and the context in which they are used.