Naruto's character development would be quite interesting in this situation. The sword could be a physical reminder of Zabuza's influence. It could lead Naruto to question his own beliefs about enemies and allies. Since Zabuza was once an enemy, receiving his sword might make Naruto re - evaluate how he views those who he once fought against. This could result in Naruto becoming more open - minded. Also, in terms of his combat skills, he could start to blend his existing ninja techniques with swordsmanship, creating a unique fighting style that would set him apart from other ninjas and further establish his growth as a character.
Well, Naruto getting Zabuza's sword could signify a new level of respect from an unexpected source. It might make Naruto more confident in his abilities as he has been recognized by a strong and feared ninja like Zabuza. This could also lead to Naruto exploring new fighting styles, incorporating the use of the sword into his combat. It could also be a symbol of Naruto's growth in the eyes of others, and it might inspire him to train harder to live up to the trust that Zabuza, in this fanfic scenario, has placed in him.
It could have a huge impact on Naruto's character. Firstly, it gives him a new tool which could change his approach to battles. He might become more versatile. Secondly, it could make him more mature as he now has to handle this gift responsibly. It might also make him think about the value of life more, as Zabuza was a complex character with his own views on life and death. And finally, it could make Naruto more of a mystery to his enemies, as they wouldn't expect him to suddenly start using a sword.