One idea could be that Naruto is transported to the Godzilla universe. He could use his ninja skills to try and communicate with Godzilla or other kaiju. Maybe he'd attempt to use his shadow clone jutsu to confuse the monsters during a battle.
Another concept is a Godzilla-like creature in the Naruto world. It could be a result of some dark chakra experiment gone wrong. Naruto and his friends would have to figure out how to stop it without getting crushed. They might need to combine their elemental jutsus to create a powerful enough attack.
Perhaps there could be a story where Godzilla comes to the Hidden Leaf Village. Naruto initially thinks it's an enemy but then realizes that Godzilla is actually there to help fight a greater evil that is threatening both the Naruto world and Godzilla's world. So they team up, with Naruto using his speed and agility and Godzilla using his brute strength.
Another possibility is that Godzilla somehow ends up in the Naruto world. The shinobi might initially see it as a great threat, but Naruto could try to communicate with it using his ability to sense emotions. Maybe Godzilla is there because it's being chased by an even greater enemy from its own world, and Naruto and his friends decide to help it.
One idea could be that Naruto characters are summoned as Servants in FGO. For example, Naruto himself could be a Berserker with his never - give - up attitude and powerful chakra being translated into high - level stats. Sasuke could be an Assassin, using his Sharingan to detect and strike enemies stealthily.
A more serious fanfic could be set in a post - apocalyptic world that was destroyed by a combined force of villains from both Naruto and Bleach universes. Naruto and Ichigo are the last hopes. They meet and initially clash due to their different ways of fighting and beliefs. But they gradually learn from each other and combine their powers in a unique way to take on the remaining villains and try to restore their worlds.
One idea could be that Venom somehow ends up in the Naruto universe. Maybe a strange rift in dimensions brings Venom to Konoha. He could initially be seen as a threat, but Naruto, with his ability to see the good in people (or in this case, symbiotes), tries to befriend Venom. This could lead to some really interesting battles and storylines, like Venom helping Naruto against powerful enemies using his unique powers.
A fanfic could be written where Alita is reincarnated in the Naruto universe as a ninja. She retains her combat skills but has to learn how to use chakra. Naruto becomes her friend and helps her adapt. They go on adventures together, facing off against powerful enemies. Alita's unique fighting style would make her stand out among the ninjas, and together they could become a formidable team.
One idea could be that Deadpool somehow gets transported to the Naruto universe. He'd be really confused at first but then start causing all kinds of chaos with his unorthodox fighting style and fourth - wall - breaking humor. Maybe he'd try to team up with Naruto, thinking he could use some of Naruto's cool jutsu in his own battles back home.
A possible fanfiction could involve Kiryu's memories of Godzilla influencing the RWBY characters. For example, Godzilla's tenacity and will to protect could inspire Ruby and her team. They could learn from Kiryu's combat techniques and use them against the Grimm. And perhaps Kiryu could be repaired and upgraded using RWBY's technology.
One idea could be a story where Naruto is somehow transported to the DxD universe and meets Ophis. He could form an alliance with her, perhaps because they both have a sense of being outsiders in the new world. Naruto's unique skills and his never - give - up attitude could influence the events in the DxD world in interesting ways.
One idea could be to have Naruto characters transported to the world of Shadow of Mordor. For example, Naruto himself could use his shadow clones in the same way the main character in Shadow of Mordor uses the wraith abilities. His clones could be used for stealth and surprise attacks, just like the wraith's powers are used in the game. It would be interesting to see how Naruto's positive and determined attitude would contrast with the dark and gritty world of Shadow of Mordor.
One idea could be to have Naruto characters trapped in the Maze Runner's maze. For example, Naruto, Sasuke and Sakura could be among the 'runners'. Naruto's determination and his ability to never give up would be a great asset in trying to find a way out of the maze. His shadow clone jutsu could be used to explore different paths simultaneously.