He could gain the ability to predict his opponents' moves more accurately. The Sharingan is famous for that. So Naruto would be even better at dodging attacks in combat.
Naruto could potentially gain the power to see chakra flow more clearly with Madara's Sharingan. This would be extremely useful in battle as he could target weak points in an opponent's chakra system. He could also use the Sharingan's ability to store and recall memories to better understand the history and secrets of the ninja world, which could give him an edge in strategic decision - making.
Naruto would likely gain the ability to use all six paths techniques. The Rinnegan allows the user to manipulate gravity, as seen when Madara used it. Naruto could use this to enhance his combat skills, for example, pulling enemies towards him or pushing them away forcefully. He could also use the Preta Path to absorb chakra, which would be a great addition to his already large chakra reserves.
The Sharingan might also give Naruto the ability to enter people's minds, at least to some extent. In the Naruto universe, the Sharingan has been shown to have some mind - related abilities. Naruto could use this to communicate with his friends in a more direct way, or perhaps even to break through genjutsu more easily. And, if he can enter the minds of his enemies, he could gather valuable information about their plans and weaknesses.
Naruto would gain the ability to copy jutsu. With the Sharingan, he could watch an opponent's movements closely and replicate their techniques. This would be a huge advantage for him in battles.
Naruto could gain the ability to manipulate light and darkness, which are often associated with Keyblades. This would be a huge change from his normal chakra - based abilities. He could also use the Keyblade to fly, giving him an advantage in both mobility and combat. Another new ability might be the power to heal, as some Keyblades have restorative properties.
In fanfiction, if Naruto got the Sharingan from Madara, it would completely change his power dynamic. He would gain the abilities of the Sharingan like enhanced perception, the ability to copy jutsu more easily, and perhaps even access to some of Madara's unique Sharingan - based techniques. This would make him an even more formidable opponent and could potentially change the entire plot of the Naruto universe within the fanfiction world.
Well, in this fanfiction, Madara could give Naruto the Sharingan as a way to balance the power in the ninja world. Naruto then uses the Sharingan's ability to predict movements in combat. This gives him an edge against enemies who are used to his regular fighting style. He might also discover some hidden abilities of the Sharingan that no one else knew. For example, it could have a unique connection to his Nine - Tails chakra, creating a whole new set of jutsus.
In some fanfictions, the Buster Sword could be enchanted. So Naruto might gain abilities like being able to send out energy slashes from the sword. These slashes could travel long distances and be very powerful, capable of taking out multiple enemies at once. Also, it could have a special connection to Naruto's chakra, allowing him to channel his chakra into the sword more effectively and use it in new and creative ways during combat.
He could develop the ability to combine the power of the Sharingan with the Nine - Tails' chakra. Maybe he could use the Sharingan to better control the Nine - Tails' power, for instance, seeing the flow of the chakra inside him more clearly. This could lead to new jutsu that are a fusion of Uchiha and Uzumaki techniques.
One possible fanfiction could be about a young ninja who discovers he has a special connection to Madara's Sharingan. Maybe he inherits some of Madara's latent powers through a mysterious family link. This could lead to him being hunted by those who want to use his power for evil or by those who fear it.
He could potentially gain an enhanced understanding of wood - style techniques. Since Hashirama was a master of it, Naruto might learn how to create more complex and powerful wood constructs, like huge forests for both offense and defense.