Perhaps a plot where the protagonist can choose to either side with the Ministry of Magic during a time of political unrest within the wizarding world or join a rebel group. This would involve different magical battles and moral dilemmas depending on the choice. In the 'harry potter cyoa fanfic', this could show different aspects of the wizarding society that we don't often see in the original books.
A really cool plot idea could be about a time - travel adventure in the 'harry potter cyoa fanfic'. The character gets the chance to go back in time to change certain events. For example, they could try to prevent the death of a minor character. But every choice they make in the past has consequences in the present and future of the wizarding world, creating a complex web of storylines.
A really unique plot idea in naruto cyoa fanfiction could be that Naruto is sent back in time to the era of the Sage of Six Paths. He could then learn directly from the originator of ninjutsu and change the course of ninja history in ways we can't even imagine. This would also give him a chance to understand the true nature of chakra much earlier and perhaps prevent some of the future conflicts in the Naruto universe.
One interesting plotline could be where Harry discovers a hidden magic that was lost for centuries. This new magic gives him unique abilities and he has to figure out how to use it without Voldemort finding out. It could change the whole dynamic of the fight against the Dark Lord.
Some 'cyoa harry potter fanfiction' stories focus on alternate timelines. For instance, if Harry had been sorted into Slytherin instead of Gryffindor. In these stories, he might have different friends, different rivalries, and a completely different path in his fight against the Dark Lord. Also, there are stories where he uses time - turners in more creative ways, changing not just his own past but the entire wizarding world's future.
Well, you could have a fanfic where Voldemort uses DND - style dark magic to open portals to other dimensions. The Order of the Phoenix has to quickly learn DND - style combat and magic rules to fight off the new threats that come through these portals. Harry could be sent on a special mission to find a DND - style mage who can teach them the counter - spells. Meanwhile, the Death Eaters are also trying to master this new form of magic for their own evil purposes. This would create a really exciting and unique story.
A cool plot for a Harry Potter Twilight fanfic could be a competition. The wizards from Harry Potter and the vampires and werewolves from Twilight compete in a series of challenges. These challenges could test both magic and the unique abilities of the Twilight characters. Or perhaps a love triangle between a Harry Potter character, a Twilight vampire, and a Twilight werewolf. It would be interesting to see how the different cultures and powers interact in matters of the heart.
Another plot could focus on the lives of the secondary characters from the original series. For example, Neville could be the head of Herbology at Hogwarts and discovers a new, dangerous plant that has some sort of connection to an ancient magic. The 'carry on fanfic' could then be about how he and his students deal with it, with some cameos from the main characters.
One idea could be that a dragon escapes from Gringotts and Harry has to use his skills to track it down. Maybe the dragon has a special connection to a powerful dark magic item that Voldemort was after.
One idea could be that Voldemort somehow enters the Runescape world to seek more power. Harry and his friends follow him there to stop him. They have to learn the rules of Runescape quickly to be able to fight Voldemort. Another idea is that a Runescape wizard discovers a portal to the Harry Potter world and brings some of the unique items from Runescape, like special runes, which causes a stir in the wizarding world.
A great plot for a Harry Potter academy fanfic might be a time - travel scenario. A group of students accidentally travel back in time to the founding days of Hogwarts. They have to navigate the different rules and attitudes of that era while also trying not to change history too much. Or perhaps there's a plot where a student is wrongly accused of a major crime at the academy and has to prove their innocence. They'll need to use their wits and the help of their friends to find the real culprit.
Perhaps in the fanfic, the snake is a key to unlocking an ancient magic that has been lost in the wizarding world. This could lead to a whole new adventure for Harry and his friends as they try to understand and use this magic.