One consequence could be a shift in the power balance. The Mountain was a powerful fighter in service of certain lords. His death would leave a power vacuum among his allies. Robb Stark, on the other hand, would gain more notoriety. His reputation as a fearsome and capable leader would spread, making his enemies more cautious of him.
Well, in the fanfiction world, Robb Stark might also get some unexpected help. Maybe there are some magical elements involved. A wizard or a sorceress could weaken the Mountain's strength or defenses. This would give Robb an edge in the fight. Then, with his courage and fighting skills, he could step in and slay the Mountain.
The Old Gods themselves would be crucial. They could be represented in various forms like the weirwood trees. And there might be some sort of priest or seer who serves as an intermediary between Robb and the Old Gods, guiding him through the spiritual experiences.
One common theme is political intrigue. Since they are from important families, many fanfictions involve them using their relationship to gain political advantages for their respective houses. Another theme is love against all odds, as their families may not approve or there could be other obstacles in their way.
Yes, there are quite a few. You can start by looking on fanfiction.net or Archive of Our Own (AO3). These platforms have a large collection of fanfictions, and you're likely to find some interesting stories about Robb Stark and Margaery Tyrell there.
One common theme is leadership. Robb Stark is a leader, so many fanfics explore how he leads his men, makes strategies, and deals with political situations.
One great 'Bran Stark x Reader' fanfic is 'A New Beginning with Bran'. It beautifully captures the unique relationship between the reader and Bran. The story shows how the reader becomes an important part of Bran's journey, and the descriptions of the Westeros setting add a lot to the overall atmosphere.
One great 'Tony Stark x Reader Fanfic' is 'The Iron Heart'. In this fic, the reader is a brilliant scientist who gets recruited to work with Stark. It has a great build - up of their relationship, from initial professional respect to a deeper emotional connection. Another good one is 'Stark's Secret Admirer' where the reader is a shy person who leaves anonymous love notes for Tony, and the whole process of Tony finding out who it is is really sweet.
There's a fanfic titled 'Robb Stark's Sister: A Tale with Theon'. In this one, the female Robb Stark character is really strong - willed. She has her own ideas about the future of Winterfell and her relationship with Theon is full of twists and turns. The author does a great job of showing how their different backgrounds shape their interactions. It's an interesting read if you like character - driven stories.