There's a fanfiction where Itachi gives Naruto a power that allows him to see through illusions more easily. This was really useful in Naruto's battles against enemies who were skilled in genjutsu. The story delved into how Naruto trained to enhance this new power and how it affected his relationships with his friends. It also had some great scenes where Naruto was able to outwit his opponents who were relying on illusions to defeat him. You can start your search for such stories on the major fanfiction platforms.
I'm not sure about a specific one off - hand, but you can check out fanfiction websites like Fanfiction.net or Archive of Our Own. Just search for 'Itachi gives Naruto power' and you'll likely find a bunch of different stories. Some might focus more on the action aspect, while others might explore the emotional side of Itachi's decision to give Naruto power.
A lot of fanfictions in this category often have Naruto using the power in unexpected ways. One that I've heard of (but can't recall the exact name) had Itachi giving Naruto a power that was linked to the Uchiha clan's history. Naruto then had to team up with Sasuke to understand and fully utilize this power. It was really interesting as it explored the relationship between Naruto and Sasuke in a new light, while also dealing with the power - up aspect. You can look for similar stories by reading reviews and summaries on the fanfiction platforms.