One idea could be a wizard discovers Beyblades in the Muggle world and decides to bring them to Hogwarts. He then challenges his classmates to Beyblade battles instead of duels. The different houses could form their own Beyblade teams and compete in a tournament, with the winning house getting extra house points and a special magical Beyblade as a prize.
A new student arrives at Hogwarts who is a master at Beyblading. He comes from a family that has a long history of both magic and Beyblading. He challenges the most popular students at Hogwarts to a Beyblade battle. If he wins, he wants to change some of the old - fashioned rules at the school. Harry and his friends are caught in the middle, not sure whether to support the new kid or the status quo.
Maybe there's a hidden chamber in Hogwarts that contains ancient Beyblades with magical powers. Harry and his friends accidentally stumble upon it. They soon find out that these Beyblades can be used to fight against dark forces that are starting to seep into the school. They have to learn how to control the Beyblades and use their magic to enhance their performance in battles.
One idea could be that during a Quidditch match, a player gets seriously injured. Instead of using magic to heal right away, an ambulance from the Muggle world is called in by a confused bystander. The ambulance crew has to deal with the magical aspects they've never seen before while trying to transport the patient to a Muggle hospital. This could lead to a lot of comical and also tense situations as they try to figure out how to handle the situation.
There could be a plot where Harry Potter as the Sorcerer Supreme has to interact with other powerful magical beings from different dimensions or realms. He might have to use his enhanced powers to protect the wizarding world from threats that come from outside their normal scope of knowledge. This could lead to all sorts of exciting adventures and challenges.
One idea could be Harry using parkour skills to escape from the Death Eaters in the Forbidden Forest. He jumps from tree to tree, slides under fallen logs, and uses his magical abilities in combination with his newfound parkour skills to outmaneuver them.
One idea could be that Voldemort discovers the power of the Stargate and tries to use it to gain more power. He could send his Death Eaters through the Stargate to conquer other worlds and bring back resources or powerful artifacts to help him in his quest to take over the wizarding world. The Order of the Phoenix would then have to follow through the Stargate to stop him.
Yes, often there are unique plots. For example, the apprentice might get involved in secret alchemy experiments Flamel was famous for. They could discover new magical potions or spells, and have adventures in the wizarding world that are different from Harry's main story in the original books.
One possibility could be that Supergirl somehow ends up in the wizarding world of Harry Potter. Maybe she's chasing a powerful magical artifact that has fallen into the wrong hands in Hogwarts. She could use her superpowers to help Harry and his friends during a particularly tough battle against Voldemort, like using her heat vision to fend off Dementors or her super strength to break through some dark magic barriers.
It's possible that a big plot twist in the fanfic is related to Harry's parents. Maybe they knew about his werewolf nature before he was born and had some sort of plan in place. Or perhaps Harry's werewolf condition was actually caused by something related to his parents' past or a secret they were hiding. This could completely change the way we view the events leading up to Harry's discovery of his werewolf side in the fanfic.
One possible plot could be that a wizard has the ability to 'rent a hero' from a magical service. Harry Potter himself could be rented out to help a young, struggling wizard face a new dark threat in the wizarding world. He could use his skills and experiences to train this wizard and together they could uncover a plot by a group of Death Eaters who are trying to revive Voldemort in a new way.
A possible plot could involve a half - fish character that was created by a dark magic experiment gone wrong. The character is found by Hagrid near the Forbidden Forest. Hagrid takes pity on them and tries to help them adapt to the wizarding world. As the story progresses, the half - fish character discovers that they have a special connection to an ancient magic that can save Hogwarts from a new and powerful dark force.
Perhaps a fanfic where Lily Potter's spirit is able to communicate with Harry Potter during his difficult times at Hogwarts. She gives him advice and guidance that helps him through his struggles, like dealing with Snape's complex feelings towards him, or facing the challenges of the Triwizard Tournament. This would add an emotional and magical element to Harry's journey.