Another idea is that the tattoo artist uses the essence of magical creatures to create tattoos. For example, a phoenix - inspired tattoo might give the wearer the ability to be reborn from ashes in a symbolic way within the story. This combines the art of tattooing with the rich mythology of Harry Potter.
Well, you could get a tattoo of a character from the fanfic in a unique pose or situation that didn't happen in the original books. For instance, if the fanfic has a scene where Harry Potter is using a new kind of magic, you could get a tattoo of him doing that. Or perhaps a tattoo of the fictional location in the fanfic that was really well - described and has a special place in your heart.
Maybe Harry Potter, as a tattoo artist, is located in a wizarding alley where all kinds of magical beings come for tattoos. He could get a visit from a centaur who wants a tattoo that symbolizes his connection to the forest. Harry would have to figure out how to tattoo the centaur's tough skin. There could also be a plot where Harry's tattoos start to have unforeseen magical effects on the wearers. For instance, a tattoo of a love potion - inspired design makes the wearer fall in love with the first person they see. Harry then has to find a way to reverse the effects while still maintaining his reputation as a tattoo artist.
One interesting idea could be tattoos that represent the Hogwarts houses. For example, a Gryffindor might have a lion tattoo. Another could be tattoos of spells, like the Lumos spell as a glowing wand on the skin. Some fanfictions might also feature tattoos of the Deathly Hallows symbols.
There's a fanfic called 'The Tattooed Wizard'. In this story, the tattoo artist is a wizard in hiding. He uses his art to secretly communicate with other magical beings. It has an interesting plot that keeps you hooked as you learn about his double life.
One idea could be a character who uses Dirty Harry - like tactics to deal with the Death Eaters. For instance, being extremely direct and fearless in the face of danger, much like Dirty Harry in his movies.
Some unique ideas could be that baby Harry has a special bond with magical creatures from a very young age. For instance, he might be able to communicate with Hedwig even as a baby, through some kind of magical telepathy. This could set up a whole different dynamic in the story.
A Harry Potter and Star Wars crossover would be really interesting. Picture Harry and his friends traveling through space in the Millennium Falcon, learning about the Force and using their magic in combination with Jedi skills to fight against a new dark threat that combines the power - hungry Sith and the dark wizards from the Potterverse.
Well, in some fanfictions, Loki might be interested in the Time - Turner device from the Harry Potter universe. He could try to use it for his own purposes, like going back in time to change certain events in the wizarding world to his advantage. Or perhaps Loki and Harry Potter get into a magical duel where Loki uses his Asgardian magic and Harry uses his wizarding spells. The contrast between their different forms of magic would be really interesting to explore in a fanfiction.
A unique idea could be that a Transformer is enchanted by a wizard to be able to use magic. So it becomes a sort of magical - mechanical hybrid. It could use spells like the wizards and also transform into different forms. For example, it could transform into a broom - like form to fly around Hogwarts.
In some 'Harry Potter Harem' fanfictions, a unique idea is to have the 'harem' members be those who have been wronged by the dark side in different ways. They bond with Harry as they all strive for justice and a better wizarding world. For instance, a character whose family was destroyed by Death Eaters joins Harry's group. This creates a deep emotional connection among the group members and a strong motivation for their actions. It also gives a new perspective on the fight against evil in the Harry Potter universe, as they work together not just for Harry's sake but for their own and the world's.