A great 'horocrux harry fanfic' could explore the idea of what if the Horcruxes had a mind of their own? Harry would not only be fighting against Voldemort but also the sentient Horcruxes that are trying to protect themselves and their master in very creative and dangerous ways.
There might be a 'horocrux harry fanfic' where Harry forms an unexpected alliance with a former Death Eater in order to figure out the secrets of the Horcruxes. This alliance could bring a whole new dynamic to the story as they both have different motives and knowledge.
It could be unique by focusing on a minor character's perspective in relation to the Horcruxes. Like Neville, who could have his own adventure involving the Horcruxes that is intertwined with Harry's but shows a different side of the story. This would give new insights into the Horcrux plot.
There are 'Harry Potter fanfic fanfic' that focus on time - travel scenarios. Imagine if a character from the later books travels back in time to the first year at Hogwarts. This can create a lot of interesting plot twists as they try to change or preserve the original story line. Also, some fanfic fanfic might center around magical creatures in a way that wasn't fully explored in the original books, like the life of a hippogriff in more detail.
A 'harry medusa fanfic' could also explore the idea of Medusa being an ancient magical being who has a connection to Harry's family. Harry discovers this connection through a series of strange events and visions. He then embarks on a journey to understand more about Medusa and how she might be related to his family's past, delving into old magic texts and seeking the advice of magical creatures.
One interesting 'Harry Charmed' fanfic could be where Harry Potter visits the Charmed Ones and they team up to fight a powerful dark wizard that has elements of both the 'Harry Potter' and 'Charmed' universes. Maybe they combine spells like the Patronus Charm with the Power of Three to defeat the enemy.
One interesting 'harry snake fanfic' could be about Harry having a special bond with a magical snake that helps him in his adventures. For example, the snake might be able to lead him to hidden secrets in Hogwarts.
One interesting 'Harry and Hedwig fanfic' could be about Hedwig saving Harry from a group of dark wizards in a forest. In this story, Hedwig uses her sharp talons and swift flying skills to distract the wizards while Harry casts protective spells.
One interesting Harry the Crow fanfic could be about Harry's adventures in a magical forest. He might encounter strange creatures and have to use his wits to survive. For example, he could meet a talking squirrel that gives him clues to find a hidden treasure.
One interesting 'horcrux harry fanfic' story could be about Harry finding a way to destroy all the horcruxes in a completely new and unexpected manner. Maybe he discovers a hidden spell that can disintegrate the horcruxes without the use of the sword of Gryffindor or the basilisk fang. Another could be a story where Harry becomes a horcrux in a different way than in the original series, and how he has to deal with the implications of that. It could involve him having to face Voldemort in a more complex psychological battle.
In some 'lucky harry fanfic' stories, Harry could be lucky in terms of his relationships. For example, he might quickly find out that Hermione has had feelings for him all along and they start a romantic relationship much earlier than in the original series, which also leads to him having more support and good luck in his adventures.
There might be a 'harry teddy fanfic' where they time - travel together. Harry and Teddy could go back in time to meet the founders of Hogwarts and learn some ancient magic. This would be a really exciting story as they face different challenges in the past.