A really fascinating pairing would be Emiya Kiritsugu from Fate and Juumonji Katsuto from Mahouka. Kiritsugu is a morally complex character who is willing to do whatever it takes to achieve his goals, while Katsuto is a more traditional and honorable magician. Their interactions could explore the different moral compasses within the context of their respective magic - filled worlds. They might initially clash due to their different approaches but eventually come to understand and respect each other.
I think a pairing between Shiba Tatsuya from Mahouka and Archer from Fate would be really interesting. Tatsuya is a very powerful and intelligent magician in his own right, and Archer has a wealth of combat experience and a complex personality. They could have some great philosophical debates about the nature of magic and the purpose of their powers.
One interesting pairing could be Miyuki Shiba and Saber. Miyuki is a strong and elegant magic user in Mahouka, and Saber is a noble and powerful Servant in Fate. They could bond over their sense of duty and loyalty. Maybe they would train together, with Saber teaching Miyuki some of her sword - fighting skills while Miyuki shares her knowledge of modern magic techniques with Saber.
Weiss and Rin could be a great pair. Both are strong - willed and come from families with a certain reputation. Weiss's elegance in combat with her Glyphs and swordsmanship could be complemented by Rin's powerful magic. They might start off as rivals, constantly trying to one - up each other, but eventually realize they can achieve more by working together.
I think Shirou Emiya from Fate and Rin Okumura from Blue Exorcist would be an interesting pairing. Shirou is a self - taught mage who is very determined, and Rin is a powerful exorcist. They could learn a lot from each other's fighting styles and magical abilities.
Akira and Minato would be an interesting pairing. Akira, with his leadership skills as the leader of the Phantom Thieves, and Minato, the protagonist of Persona 3, could share their strategies in combat and dealing with the Metaverse. They both have different experiences with their respective groups, so they could learn a lot from each other.
The Arbiter and Thor. Thor is a powerful Asgardian with his hammer and lightning powers, while the Arbiter is a skilled warrior from the Halo universe. They could fight side by side against a common enemy. Their different cultures and fighting styles would make for an exciting combination. Maybe Thor could teach the Arbiter about magic, and the Arbiter could show Thor some unique Covenant combat techniques.
Another great pairing could be Rin Tohsaka and the Shield Hero. Rin is a skilled mage in the Fate universe. She could help the Shield Hero understand the magic in the Fate world, and in return, the Shield Hero could show her some of his shield - based techniques that might be useful in combat. Plus, their different personalities would lead to some interesting interactions.
One of the most interesting pairings would be Saber and Elsa. They are both strong female characters with powerful magic. Saber could teach Elsa about combat and leadership, while Elsa could show Saber how to better control her magic in a more natural way. Also, Kristoff and Lancer could be an unexpected but interesting pairing. Lancer's pride and Kristoff's down - to - earth nature would create some fun interactions.
Spiderman and Green Lantern. Green Lantern's power ring can create all kinds of constructs, and Spiderman could use his webs to enhance or modify those constructs. They could work together to build a huge structure to stop a giant alien invasion that is threatening both the Marvel and DC universes.
Ruby and Church could be an interesting pairing. Ruby is young and idealistic, while Church is often sarcastic and has a more jaded view. Their interactions could be really fun to read. Another would be Weiss and Tucker. Weiss is from a high - society background and Tucker is, well, Tucker. The contrast in their personalities and upbringing would make for an engaging story.
Oliver Queen and Dean Winchester would be an interesting pairing. Oliver is used to leading a team and taking on tough enemies in his city. Dean is a no - nonsense hunter. They could have some great banter and learn from each other's combat and survival skills.