Connor MacLeod from Highlander. If he entered the Harry Potter world, his warrior skills and centuries - old wisdom would be fascinating. He could teach the young wizards about different forms of combat that don't rely solely on magic. And his experiences of living through different eras could give the wizards a new perspective on history and the importance of their own battles.
Hermione Granger would be a great choice too. Her thirst for knowledge would lead her to study the lore of the Highlanders intensively. She could figure out ways to use magic to either protect Immortals or find a way to end the immortality curse if she saw it as a danger. Her intelligence would make her a force to be reckoned with in the Highlander's world.
Well, perhaps there's a Highlander who stumbles into the wizarding world. He might be confused at first by all the magic but then realizes he can use his immortality and combat skills to his advantage. He could get involved in the fight against Voldemort, using his unique abilities. Or, there could be a magical tournament in the Harry Potter world that also includes Immortals from the Highlander world, and they compete using both magic and their Highlander powers.
Definitely Harry Potter and Ichigo. Harry is used to dealing with the mystery and danger in the wizarding world, while Ichigo has his own battles against Hollows and the like in Bleach. Their different powers and personalities would create a great dynamic. They could learn from each other's strengths and overcome their weaknesses together. Another interesting combination could be Hermione and Rukia. Hermione's intelligence and knowledge of magic could be paired with Rukia's experience as a Soul Reaper.
I think Hermione would be the most interesting. She's highly intelligent and resourceful. In 'The Force Awakens' world, she could use her vast knowledge of magic to analyze and perhaps even enhance the technology there. She might also be able to come up with unique strategies against the First Order using her magical skills, like creating illusions to deceive the enemy or using spells to protect the Resistance bases.
Draco Malfoy and Kaname Kuran could be an interesting pair. Draco is from a wealthy and powerful pure - blood wizard family, and Kaname is a powerful pure - blood vampire. They both have an air of superiority about them. It would be interesting to see how they interact, whether they become rivals or somehow find common ground. Maybe Draco would be intrigued by Kaname's vampiric powers and try to use them for his own gain, or Kaname might see Draco as a useful ally in his own plans.
I think Michael Corvin could be an interesting crossover character. He's a hybrid in the Underworld series, which means he has a unique set of abilities. In the Harry Potter world, he could be seen as a strange new kind of magical being. He might be able to help the wizards understand different types of magic that are more physical and instinct - based like his own. Also, his journey of self - discovery in the Underworld could be paralleled in the wizarding world as he tries to find his place among the wizards and witches.
Sam Carter and Methos would be a fascinating combination. Sam's scientific genius could be intrigued by Methos' ancient knowledge and long - lived existence. Methos might also be able to offer some unique perspectives on the technology Sam deals with in the Stargate program, and together they could come up with innovative solutions to problems.
It could be Aquaman. He is so different from the wizards in the Harry Potter universe. His fish - like abilities and his role as a king would make for some great interactions with the Hogwarts students and professors. He could teach them about the ocean and its secrets, while also being amazed by the magic of wands and potions.
Percy would be really interesting. His ability to control water and his laid - back yet brave personality would contrast well with the more formal wizarding world. He could make some really funny and unexpected interactions with the Hogwarts students and teachers.
Hermione would be really interesting. She could bring her intelligence and knowledge of magic to the iCarly crew. Imagine her helping Freddie with his tech projects using magic, or teaching Carly and Sam some basic spells. It would be a great contrast between the magical and Muggle worlds.
Hermione and Death could be an interesting pairing. Hermione is known for her intelligence and thirst for knowledge. Death, being an all - powerful entity in the Darksiders universe, could have a lot of knowledge that Hermione would be eager to learn. Their conversations would likely be deep and thought - provoking as she tries to understand the nature of death from his perspective.