One idea could be a crossover where Naruto and Hinata somehow end up in the Bleach universe. Maybe they are mistaken for powerful spirits and are recruited by the Soul Society. They could use their ninja skills in battles against Hollows. For example, Naruto's Rasengan could be a powerful attack against Hollows, and Hinata's Byakugan could help in detecting spiritual presences.
Another concept is that a Hollow with the ability to travel between universes attacks Konoha. This Hollow has the power to absorb chakra. Naruto and Hinata, along with some Bleach characters like Ichigo, team up to stop it. Hinata might use her Gentle Fist techniques to disrupt the Hollow's chakra - absorbing ability, while Naruto and Ichigo go for a full - on offensive with their signature moves.
A more complex fanfiction could involve a forbidden jutsu in the Naruto world that accidentally opens a portal to the Bleach world. Naruto and Hinata are the first to be sucked in. In the Bleach world, they meet Rukia, who teaches them about the spiritual energy there. Hinata starts to develop her own spiritual powers, similar to how she developed her ninja skills, and Naruto tries to find a way back home while also getting involved in the conflicts between Soul Reapers and Hollows.
One idea could be a crossover where characters from Naruto, Shiba (assuming you mean the Shiba clan from Bleach) and Bleach meet in a new dimension. For example, Naruto characters could be transported to the Bleach universe and interact with the Shiba clan members. They could team up to fight a common enemy, like a new powerful Hollows or Akatsuki members who have also found their way into this new world.
Perhaps in this fanfiction, the Espada from Bleach are somehow related to the nightmares in My Little Nightmare. The Espada could be using the nightmares as a way to gain more power, and the protagonists from both worlds have to team up to stop them. This would create a really interesting dynamic between the two very different universes.
One idea could be to have characters from Naruto end up in the world of Danmachi. For example, Naruto himself could find his way into the dungeon and his ninja skills would be put to the test against the dungeon monsters. His shadow clone jutsu could be used in interesting ways, like sending clones into different dungeon levels to scout or fight. Another idea is to have the concept of chakra introduced into the Danmachi world. This could change the way adventurers fight and level up. Maybe some of the Naruto characters could train the Danmachi adventurers in new combat techniques.
One idea could be a crossover where Naruto is somehow transported to the Star Wars universe and meets Padme. Maybe he uses his ninja skills to protect her from the Sith.
Another concept is that Naruto is sent to Middle - earth. There, he could use his ninja skills and chakra powers. He and Gandalf could team up to fight Sauron. Naruto's ability to make friends and inspire others would be really useful in uniting the different races of Middle - earth against the common enemy.
A more complex idea is that the Matrix is used to create a virtual training ground for the shinobi. They enter the Matrix to practice their skills in a more controlled environment. However, they soon realize that there are some dark secrets within the Matrix, and Naruto has to lead the way to uncover the truth and free those who are trapped inside.
Another possibility is that Naruto visits the Townsville, the city where the PPG live. He might be confused by the modern technology there compared to his own world. The PPG could teach him about it while he shows them some of his ninja skills like tree - climbing and water - walking.
A third idea could be a story where Naruto's clones are mistaken for some kind of superpower by the Thundermans. Max might be intrigued and try to figure out how to do it himself. Meanwhile, the Thundermans could teach Naruto about modern technology which he has never seen in his own world. This could lead to some really interesting and comical situations as they try to understand each other's worlds.
Another possibility is that Pokemon exist in the Naruto world. Some ninja could have Pokemon as partners instead of traditional ninja animals. For example, Sasuke could have a Dark - type Pokemon like Umbreon that would match his cool and mysterious personality. And the Pokemon battles could be incorporated into the ninja battles, adding a new layer of strategy.
One idea could be a crossover where Naruto characters gain the abilities of Needless characters. For example, Naruto could get the power of Adam Blade's regeneration. It would be interesting to see how he uses it in battle, especially against tough foes like Pain or Madara.