A simple plot could be that Harry goes to London for a Quidditch tournament. While there, he gets lost in the city and stumbles upon a hidden wizarding library that contains ancient spells and prophecies. He then has to figure out how to get back to the tournament while also dealing with the knowledge he has gained from the library.
Perhaps the fanfic is centered around a new school in London for magical creatures. Harry is invited to be a guest lecturer there. While teaching, he realizes that some of the magical creatures are being mistreated by a group of rogue wizards. Harry decides to take action and with the help of the students and the school's faculty, he sets out to expose the rogues and protect the magical creatures. This would involve Harry using his knowledge of the wizarding world and his experience with magical creatures from his own adventures.
In a London - named Harry Potter fanfic, it could be set in an alternate London where the wizarding world is more integrated with the Muggle world. Harry could be part of a secret society in London that protects both worlds from a new dark magic threat. This would involve him teaming up with new characters, both wizard and Muggle, and using his skills and knowledge to keep the city safe.
Perhaps it's a business - related fanfic. People from different companies come to London for a meeting. There could be power plays, secret alliances being formed, and unexpected revelations during this London meeting. For example, a young entrepreneur might meet a big - shot investor at the meeting and try to convince them to invest in their startup.
The plot might involve Harry being in the rent boy business not entirely by choice. He could be under some sort of spell or coercion. When he sees Snape in trouble, it could be a turning point for him. Snape, on the other hand, might initially be shocked to be rescued by Harry, but then realizes that Harry has more to him than meets the eye. They could then form an unlikely alliance to deal with the underlying threats in London's wizarding underworld.
The fanfic could center around Harry's life outside of the main events of the books. For example, it could explore his summer holidays in more detail. He could be spending time in the Muggle world and using his magic in creative ways to solve normal, everyday problems. He might use magic to help his neighbor fix a broken fence without the neighbor realizing it was magic. This would add a new dimension to his character and show how he can adapt his magical abilities to different situations.
One possible plot could be that Harry Potter is hired by Sherlock Holmes to help with a case that involves dark magic. Harry uses his knowledge of the wizarding world to uncover clues that Sherlock couldn't find with just his deductive skills.
Imagine Harry Potter as a bartender. He could be using his skills not just in mixing drinks but also in reading people. Since he has faced so many challenges in his life, he can easily spot if a customer is hiding something or if they are in trouble. His bar could become a place where secrets are shared, and he has to use his wits and magic to keep things in order. He might also have to deal with rival bartenders from other wizarding establishments who are jealous of his popularity and unique drinks.
The plot could involve Harry Potter discovering he has some sort of connection to a dragoness. Maybe he can communicate with her telepathically. They could team up to fight against dark forces in the wizarding world. For example, Voldemort might be after the dragoness for her powerful magic, and Harry has to protect her while also using her strength to defeat Voldemort.
One possible plot could be a deaf Muggle - born student getting their Hogwarts letter. They face difficulties in the beginning as they can't hear the instructions well. But they soon discover a magical device that helps them 'hear' in a magical way, like through vibrations that translate into words in their mind. Then they go on to prove themselves in classes like Charms and Potions, making friends along the way.
Well, it could be that Harry discovers a hidden chamber in Hogwarts that has Xenomorphs in it. Maybe he has to use his magic to fight them off or find a way to co - exist.
Well, perhaps the Hitman gets transported into the Harry Potter universe by some sort of magic accident. He then uses his combat and assassination expertise to help Harry Potter and his friends in their fight against Voldemort. He could teach them some non - magical ways of combat and they could teach him about magic in return. This would create an interesting dynamic between the Muggle - like Hitman and the magical characters.