I'm not sure if there's a super - popular one specifically about Harry riding Snape. Fanfiction is a vast world and while there might be some out there with this concept, it's not as common as some other themes. However, in the general realm of Harry Potter fanfiction, there are so many creative and unique stories that it's possible someone has written such a thing.
In a possible fanfiction plot, perhaps Harry discovers a magical spell that allows him to 'ride' Snape in a sense of using Snape's magic or knowledge for a quest. Maybe it's a situation where Snape is under a spell himself and Harry has to control him like a steed to reach a hidden place in Hogwarts to find a powerful artifact that can save the wizarding world.
A lot of fanfic writers will create unique storylines for Snape's courtship. They might introduce an original character who manages to break through Snape's tough exterior. His courtship would then involve him struggling with his own insecurities and his reputation. This character might see the good in him that others overlook. There could be moments of tension and misunderstanding, but also deep, meaningful conversations as they get to know each other better.
Often in fanfiction, the ring can be a plot device. It could be that Harry Potter unknowingly has a connection to the ring, and Severus Snape has to keep it from falling into the wrong hands. This creates a situation where Snape has to protect both Harry and the ring, leading to some tense and interesting storylines.
In some fanfictions, Snape might share some of his knowledge about the wizarding world's secrets with Harry. Maybe he tells Harry about certain spells or magical artifacts that could help Harry in his fight against Voldemort. This act of sharing knowledge is a way of being nice as it gives Harry an advantage in his battles.
One great fanfiction is 'The Prince's Tale Reimagined'. It delves deeper into Snape's relationship with Harry from Snape's perspective. Another good one is 'Snape's Redemption Arc'. It shows how Snape's actions throughout the series can be seen in a different light, with a focus on his complex relationship with Harry. And 'A Different Kind of Magic' is also a wonderful read. It creates an alternate universe where Snape and Harry have to work together more closely from an earlier point in the story.
One appeal is the novelty. It's not something you'd expect in the normal Harry Potter world, so it grabs attention. Fans like to see familiar characters in new and unexpected situations.
In some Harry Potter fanfictions, the concept of Severus Snape being mpreg (male pregnancy) is a rather unique and creative idea. It often explores different aspects of Snape's character in new and unexpected ways. For example, it might show a more vulnerable side of him as he experiences the physical and emotional changes that come with pregnancy. Some fanfictions use this concept to build deeper relationships between Snape and other characters, like Harry Potter himself, who could be involved in a more complex dynamic with a pregnant Snape.
Fanfiction about Severus Snape courting Harry Potter can range from quite romantic to more of a platonic exploration of their connection. Some fics might focus on Snape's redemption arc and how his feelings for Harry develop over time. It could also be a way to rewrite the somewhat tragic and unfulfilled aspects of Snape's life in the original books. However, it also needs to be done carefully to stay true to the essence of the characters and the magical world that J.K. Rowling created.
One idea could be that Snape takes Harry in secretly. He teaches Harry advanced potions and magic in a more personal way, away from the prying eyes of Hogwarts. Harry begins to see Snape in a new light, not as the mean professor but as a strict yet caring guardian.