John Wick could be a unique crossover character. He is known for his incredible combat skills in a more modern, urban setting. Big Boss and John Wick could cross paths in a mission that has something to do with a powerful criminal organization. Their different fighting styles and moral compasses would lead to some really interesting interactions.
Solid Snake is an obvious choice. Since they are from the same general franchise, their encounter could be filled with a lot of drama and action. They could have different views on how to handle certain situations, which would create great story tension.
One potential crossover character could be Harry Potter. Imagine Naruto, with his immortality, meeting Harry in the wizarding world. Naruto could teach Harry some ninja skills, and they could fight together against Voldemort. Another could be Superman. The contrast between Superman's superpowers and Naruto's ninja skills, along with Naruto's immortality, would make for an interesting story.
Maybe Naruto from Naruto could be a crossover character. His ninja skills and Ichigo's combat abilities could create some unique fight scenes. Also, their different ideologies about friendship and power could lead to some great character interactions.
Characters from 'Teenage Mutant Ninja Turtles' could be great. Imagine the Ducks and the Turtles teaming up to fight a common foe in the streets of New York. The Turtles' martial arts skills combined with the Ducks' hockey moves would make for an exciting story.
King Kong would be an obvious choice. The epic battles between Godzilla and King Kong are well - known, and a fanfiction could explore different scenarios of their encounters, like what if they had to team up against a greater threat.
One potential crossover character could be Goku from Dragon Ball. Since Naruto has godlike powers in this scenario, a meeting with Goku, who also has superhuman strength and abilities, would be very interesting. They could have a friendly sparring match or team up against a common enemy.
Goku from Dragon Ball could be a great crossover character. His Saiyan powers and love for combat could contrast and interact in an interesting way with Naruto's ninja skills and immortal sage abilities. They could have epic battles or team up against a common enemy.
Definitely Sherlock Holmes. Since The Great Mouse Detective is inspired by Sherlock Holmes, a crossover with the original Holmes would be very interesting. They could compare and contrast their detective methods.
Well, if we consider other shonen - style series, someone like Naruto from 'Naruto' could be a potential crossover character. His ninja skills and strong will could create some interesting dynamics with the 'world trigger' characters.
One potential character could be Naruto from the Naruto series. His ninja skills and strong will could create an interesting dynamic with 'godlike gon'. Another could be Goku from Dragon Ball. The comparison of their power levels and fighting styles would be really cool. Also, maybe Light Yagami from Death Note. The clash between 'godlike gon's sense of justice and Light's more morally ambiguous actions would make for an exciting story.
Rukia could be one of the characters. Since she has a deep connection with Ichigo already in the original series, it would be easy to develop a more romantic aspect in the harem setting. Orihime is also a likely candidate, as she has strong feelings for Ichigo. And from other animes, a character like Saber from 'Fate/stay night' could be interesting. Her noble and powerful nature would contrast with Ichigo's more rough - around - the - edges personality.