Kikoku is the name of Trafalgar Law's sword. It is a "Cursed Sword", though is not a ranked blade.

Kikoku is a larger version of the katana known as an Ōdachi. It has an oblong-shaped hilt trimmed with short white fur, a purple grip with two white rings around it and a yellow pommel, sheathed in a black scabbard decorated by white crosses from the opening to the bottom, and with a small piece of red rope tied near its opening.

Due to its size, Law usually carries Kikoku over his shoulder (in contrast to other sword-wielding characters in the series, who either carry theirs on their hips or over their backs); yet in other times, he delegates one of his crewmates (Bepo) to carry it for him.

Abilities

Most of Kikoku's actual capabilities are unknown, as more often than not, Law combines it with his Ope Ope no Mi powers, serving as a "scalpel" to cut people or as an "injection needle" to pierce others. At full power, he could bisect an entire mountain and a meteor. Alone, Kikoku was durable enough to block Doflamingo's strings, a notable feat as most weapons since then were easily cut by these strings unless they were infused with Busoshoku Haki.

Techniques

Amputate: Law's basic offensive technique. Law cleanly cuts his target with Kikoku without actually harming them. Law's sword doesn't actually have to make contact with the enemy to cut the target apart. The separated body parts seem to maintain a connection similar to Buggy when using his Bara Bara no Mi powers. While Law has never called this technique before using it, he named it while explaining Radio Knife. Amputate also seems to be necessary when performing operations, in order to extract narcotics from patients, as he did so on the drug-addicted children on Punk Hazard. Law first demonstrated this move against a Marine soldier outside the Human Auctioning House in the Sabaody Archipelago, using it in combination with "Shambles". An "amputation" is the removal of a body extremity by trauma, prolonged constriction, or surgery.

Injection Shot: While aiming at his target with a targeting reticle similar to his Scan that appears on his hand or blade, Law rushes towards them with his sword stretched out in order to stab them. Once the sword connects, Law makes it "fire" like a gun, making the target bleed in the aimed spot while pushing them back a fair distance. Law's signature ability of being able to cut objects from afar can still be used while performing this move, as seen when he cut through Trebol's Hanamizu Shinken Shirahadori without having to touch it with his sword, but the move can still be blocked by hitting the blade from the side. It was first used against Trebol, but was interrupted by Doflamingo before it made contact. Its first successful use was against Doflamingo himself.

Sterben: A technique used when Law had his right arm severed by Doflamingo. After using Takt on his severed arm, Law makes it spin. Because the arm is still holding Law's sword, it effectively ends up acting like a buzzsaw that cuts the opponent in a vertical motion. It was first used to defeat Trebol. Sterben means "to die" or "dying" in German, often used as a term for hospital deaths. In the FUNimation dub, it's called Sterben Blade. The kanji is read literally as "katana".