One idea could be a story where a new character discovers they have a unique fire - based ability that is different from the typical fire jutsu in Naruto. They could struggle to control it at first, causing chaos in their village, but then learn to harness it with the help of an old master.
First, decide on the main character. If it's an existing Naruto character, think about how you can expand on their relationship with the fire element. For example, if it's Sasuke, you could explore how his use of fire changed after certain events. Then, create a conflict. It could be an external threat like a new enemy with a counter to fire jutsu, or an internal struggle like a character losing control of their fire element.
One idea could be a crossover where Naruto's world is invaded by a threat from Hawkgirl's universe. Naruto, with his determination and powerful jutsu, teams up with Hawkgirl, who has her mace and flight abilities. They start off not trusting each other due to their different backgrounds but gradually learn to work together as they face the common enemy.
There's also the 'Inferno Storm Jutsu' in some fanfictions. It creates a large - scale storm made entirely of fire. The fire in this storm has different intensities, with the center being the hottest and most destructive. It can cover a large area, making it a great offensive move against groups of enemies.
A very creative 'Naruto' fanfic idea could be a time - travel one. For example, Naruto travels back in time to prevent the Uchiha massacre. Another idea is a fanfic where the ninja world is merged with the fairy - tale world. So Naruto could be fighting against the Big Bad Wolf or teaming up with Cinderella. And a fanfic where the Sharingan has a completely different power, like the ability to control the weather, would also be a very creative concept.
A plot could be that a succubus is sent to the Naruto universe as part of a deal between dark forces. She targets Naruto because of his growing power. But as she gets closer to him, she starts to feel real emotions for him instead of just using him for power. This creates a conflict within her as she has to choose between her original mission and her new - found feelings.
One idea could be Naruto swapping bodies with Kakashi. Naruto would then have to deal with Kakashi's more laid - back attitude towards life while also handling his responsibilities as a teacher. He might also be able to learn some new jutsu from Kakashi's memories. Another idea is Naruto swapping with Gaara. This would be interesting as they both have had very different upbringings and Naruto could understand Gaara's pain more deeply. It could also lead to a better understanding between the two villages.
A fanfiction could explore what if the Gunbai was not just a weapon but a key to a different dimension. Naruto accidentally activates it and finds himself in a strange world filled with old - time ninja and powerful beasts. He has to find a way to get back to his own world while also dealing with the mysteries of this new place and the role the Gunbai plays there. This story could involve Naruto learning new jutsu and making new friends along the way.
One creative idea is the combination of Sentai's mecha with Fire Emblem's mounts. Imagine a giant mecha replacing a pegasus knight's mount or a dragon. It completely changes the battle dynamics and visuals. Another is the way Sentai teams can use their group attacks in Fire Emblem - style battles, adding a new layer of strategy.
You could also write a fanfiction about Naruto being raised by a different clan in the village. For example, if he was raised by the Uchiha clan, it would have a huge impact on his character development and relationships within the village.
The concept of bringing the villains from both universes together is also quite creative. For example, Orochimaru and Lord Farquaad teaming up against Naruto and Shrek. It creates a whole new dynamic and a lot of interesting plot twists as the heroes have to figure out how to defeat this unexpected alliance.