Maybe in the fanfic, Harry is forced to play the role of a doctor during a wizarding war. He has to quickly learn how to heal the wounded soldiers on the battlefield. This could involve him using his knowledge of magic in innovative ways and also facing moral dilemmas about who to save first. It would be a story full of action and tough decisions.
I'm not sure specifically which 'Harry Potter plays doctor' fanfics are out there. But you can try searching on popular fanfic websites like Archive of Our Own (AO3). They have a large collection of Harry Potter fanfics and you might be able to find something related by using relevant keywords in their search bar.
Well, it could be that Harry Potter discovers he has a connection to Sparda. Maybe he has some latent power that is related to Sparda's abilities. He then has to learn to control this new power while still dealing with the threats in his own wizarding world. And perhaps he uses his new - found powers to fight off dark wizards in a more badass way.
In a fanfiction, Harry could be transported to the Pokemon world while on a mission for the Order of the Phoenix. There, he learns about Pokemon battles and uses his magic in unique ways to train and battle with his Pokemon team. He might also find that some Pokemon have a natural affinity for magic, and together they form an unbeatable combination.
One idea could be to create a story where a new student arrives at Hogwarts with a unique and powerful form of magic that no one has seen before. This could lead to all sorts of adventures and challenges as they try to fit in while also dealing with those who might be jealous or afraid of their power.
One possible plot could be that a new, extremely powerful and irresistible poison is created by a dark wizard. The main characters, like Harry, Hermione, and Ron, have to find an antidote before it spreads and kills many students at Hogwarts.
Perhaps it's a fanfic that takes the concept of Persephone's abduction in Greek mythology and applies it to the Harry Potter universe. The 'his' could be a dark wizard who kidnaps Persephone, a powerful witch, and the plot could be about her friends in Hogwarts trying to rescue her. Or it could be a more romantic take, where 'his' is a hero - type character and Persephone is in some sort of danger related to the ongoing battle between good and evil in the wizarding world, and he has to save her.
The plot could be about Harry Potter taking a nightly stroll in the Forbidden Forest. He might be feeling restless and decides to explore on his own. During the stroll, he stumbles upon a rare magical creature that he's only read about in books. This encounter could lead to a new adventure as he tries to protect the creature from other threats in the forest.
In a 'Harry Potter is a fighterback in time' fanfic, the plot could involve Harry going back in time for various reasons. It could be to save someone who died in the original timeline, like Sirius Black. He would then have to face the challenges of the past while also trying not to disrupt the future too much. He might also have to deal with the younger versions of his friends and teachers, and how they react to his knowledge from the future. And of course, he would be fighting against the threats of that time period, which could include Death Eaters or other dark wizards. He would need to use his skills and magic in new ways, adapting to the different time and its rules.
One idea could be exploring what would happen if Harry had a twin sister who was sorted into Slytherin. It would add a whole new dynamic to the story, with her having different views and friends than Harry. She could be caught between loyalty to her house and loyalty to her brother.
One idea could be that the Plague Doctor arrives in the wizarding world during a mysterious illness outbreak. He might have unique magical remedies that are different from what the wizards are used to. Maybe he teams up with Harry Potter to find the source of the disease, which turns out to be a dark magic - created pathogen.