This is a simple chakra blade that the users of Susanoo are capable of creating and wielding, and just like the Susanoo itself, each particular blade is unique to the individual involved. Despite their variations, each sword is extremely effective, and as Susanoo evolves, so does the sword.
Sasuke Uchiha's Susanoo is capable of utilising a blade resembling a sabre, wielded by its primary left arm. Sasuke was able to use it to cut through several stone pillars with ease.
Upon reaching its final form, the composition of the chakra orb held by the secondary right arm of Sasuke's Susanoo changed to that of Amaterasu's black flames, from which Sasuke is able to forge into the shape of a blade that his Susanoo's primary right arm wields.
Madara Uchiha's Susanoo possessed two distinct, undulating blades, which resembled kris. The blades were held by the right arm of both sides of his Susanoo in its incomplete and complete forms, and one could even be materialised while only surrounded by his Susanoo's aura. In the anime, the blades left a blue fire in the ground after impacting, and upon gaining its other two swords on top of its massive physical strength it could unleash tremendous shock waves which obliterated hundreds of shinobi in a single strike. In its final form, the size of the blades increased dramatically, and were wielded by its primary right arm and primary left arm. In the anime, Madara could manifest swords in all four of the arms, but the first two blades, instead of one being held in each part of the Susanoo's right arm, were held by both arms of the same side's Susanoo.
When Madara stabilised his Susanoo's final form, the blades more closely resembled traditional katana, complete with sheaths. Said sheaths were held with his Susanoo's secondary arms, while the swords were wielded with its primary ones. Madara could use these to cut through a range of mountains in the distance with a single swing. The blades could also be partitioned to a Tailed Beast Ball during its formation, giving it cutting power. Madara did so to prevent Hashirama Senju from grabbing Tailed Beast Balls with his Wood Release: Wood Human Technique.
Itachi Uchiha's Susanoo wielded a blade which was curved in nature and resembled a dagger or tantō rather than a sword. Itachi demonstrated the ability to manifest this blade while only forming his Susanoo's ribcage and arms, during his battle against Kabuto Yakushi. With it, he was able to cut through Kimimaro's bones, which were stated to be harder than tempered steel.