The Arbiter is another character. Given his complex relationship with the Covenant and his newfound alliance with the UNSC in the Halo series, his perspective would add depth to a crossover story. He could provide valuable insights to Noble 6 about the Covenant's inner workings and help in diplomatic situations if needed.
Master Chief is a common character paired with Noble Six. Given their both being iconic Halo characters, fans like to imagine how their different combat styles and personalities would interact. Master Chief's stoic and experienced nature could contrast or complement Noble Six's own skills and traits.
Definitely, Cortana could be a main character in a 'halo anime crossover fanfiction'. If she were in the world of Code Geass, she could help Lelouch with his strategic plans, using her vast knowledge and intelligence. Another option is the Elites from Halo. They could be the main characters in a crossover with My Hero Academia. Their physical strength and warrior culture could be contrasted with the superheroes in that anime, and they could have some interesting interactions with the students at UA High.
Master Chief could be an obvious choice for the human side. He's a well - known and powerful character. For the Covenant, the Arbiter would make a great main character. Their different perspectives and skills could create an interesting dynamic.
Well, from 'Supernatural', Sam and Dean Winchester could be involved. They could bring in a case where they suspect a supernatural cause for a patient's illness. Shaun would be skeptical at first but then start to see things in a new light as they investigate. It would be a mix of the medical and the supernatural worlds.
Obviously, Harry Potter could be one of the main characters. He could be the one to bridge the gap between the two worlds, using his courage and magic skills. Master Chief from Halo is also a great candidate. His combat experience and leadership would be valuable in the wizarding world full of new threats. Hermione would also be important as her intelligence could help in understanding the Halo technology.
The Spartans from Halo would also be great main characters in this crossover. Their super - human abilities and combat training would make them stand out in the Supreme Commander world. They could be the ones to teach the Supreme Commander forces about hand - to - hand combat and stealth operations, which are not as emphasized in the Supreme Commander gameplay.
Master Chief from Halo is an obvious choice. His super - soldier skills and stoic nature would be really interesting to see in the Mass Effect universe. Another one could be Commander Shepard from Mass Effect. Putting Shepard in the middle of a Halo - style conflict would be exciting. And Cortana, the AI from Halo, could also play a major role. Her intelligence and relationship with Master Chief could be explored in new ways when combined with the Mass Effect elements.
One interesting concept could be the combination of different Halo universes or timelines. For example, seeing how Noble Six would interact with characters from other Halo installments. Maybe Noble Six gets thrown into a situation where they have to team up with enemies from another part of the Halo world due to some strange anomaly. This could lead to some really cool character development and action scenes.
Another plot could involve Noble 6 having their consciousness transferred into a Forerunner construct in a crossover. This would force them to navigate Forerunner technology and politics while still trying to uphold their UNSC values. They could form an unlikely alliance with a Forerunner AI to stop a rogue element within the Forerunner society.
Naruto himself would be a key character. His relationship with Kakashi is a central part of the original story, so seeing how he reacts to an evil Kakashi would be fascinating. Sasuke could also be involved. He and Kakashi have a complex relationship, and an evil Kakashi might try to manipulate Sasuke further for his own dark purposes.