A great plotline could be Snape training Draco in advanced potions and magic that are not part of the regular Hogwarts curriculum. This could lead to Draco having unique skills that help him in the wizarding world. Also, Snape might take Draco on secret excursions to learn about the history of the Dark Arts in a way that doesn't lead him down a dark path but rather makes him understand the dangers better.
There could be a plot where Snape discovers Draco has a talent for something unexpected, like healing magic. Snape then encourages Draco to pursue this, which goes against the expectations of the Malfoy family. This causes a rift between Draco and his family at first, but with Snape's guidance, Draco learns to balance his newfound passion with his family obligations.
Some fanfics have a plotline where Draco becomes a double agent, and Snape has to protect him while also dealing with Harry's suspicions. It creates a really tense and interesting dynamic between the three.
One possible plotline could be Iruka and Kakashi trying to teach Naruto different ninja skills in their own unique ways. For example, Kakashi might focus on more advanced combat techniques while Iruka helps Naruto with the basic ninja knowledge. Another plotline could be them dealing with Naruto's pranks and how they discipline him in a loving yet firm manner. Maybe they also have to protect Naruto from some of the more dangerous elements in the ninja world that target him because of his status as the Jinchuriki.
A third plotline could be Snape falling in love during his time as a Death Eater. He meets a witch in Voldemort's inner circle who is also having doubts about their loyalty to the Dark Lord. They bond over their shared misgivings and a desire for something more than the life of a Death Eater. Their love gives Snape the strength to secretly work against Voldemort.
One possible plotline could be exploring Snape's internal struggle as he endures Lily's bullying. He might be torn between his feelings for her and the pain she causes. Another could be Lily's realization of her wrongdoings and her journey to make amends.
Well, in some fanfictions, Snape might be trapped in a magical trap set by Death Eaters who are still loyal to Voldemort's ideals. Harry, with his natural sense of justice and his loyalty to Hogwarts (where Snape also has a complex connection), figures out the trap's mechanism and manages to free Snape. Or perhaps Snape is on the verge of being attacked by a magical creature, and Harry, using his experience with magical creatures from Hagrid's teachings, scares the creature away and saves Snape.
One possible plotline could be that Harry confesses his long - hidden feelings of friendship. Maybe after years of rivalry, he realizes Draco has a different side and he wants to start anew. He might confess in a moment of great danger, like when they are both facing a common enemy. This confession could lead to an uneasy alliance at first, as Draco is shocked but then slowly warms up to the idea of a real friendship with Harry.
A common plotline is an alternate universe where Snape is not as bitter and Hermione befriends him more easily. They could be involved in a battle against a new dark force, and their combined intelligence and magic powers are crucial for victory. Also, there could be a plot where Hermione accidentally enters Snape's mind through some experimental magic and discovers his deepest secrets, which then changes their relationship.
One plotline could be Naruto teaching his sister ninjutsu. Since Naruto has his own unique skills like the Rasengan, he could pass on some basic forms of it to his sister. Another could be Naruto protecting his sister from the village's initial distrust, just as he faced it himself. Maybe he has to stand up to the village elders to ensure his sister gets a fair chance at becoming a ninja.
One interesting plotline could be Thranduil teaching Legolas how to hunt. Thranduil, being a skilled hunter, would pass on his knowledge to the young Legolas. He could start with teaching him how to track small animals in the forest. Another could be about Thranduil introducing Legolas to the different cultures within their realm. This would help Legolas understand the various elves and their ways, which would be important for his future role as a prince.
Perhaps a plotline where Snape's heart leads him to question his loyalty to Voldemort. As he becomes more in touch with his emotions, he realizes the true horror of the Dark Lord's actions. This could lead to him secretly working against Voldemort in a more direct way than in the original story. He may also find himself in the middle of a moral dilemma as his new - hearted self clashes with his past actions.