Daenerys Targaryen would be fascinating. She has her own dragons, but Lightbringer could be the key to truly uniting the people of Westeros under her rule. It could symbolize her rightful claim to the Iron Throne and be a tool to overcome any remaining opposition.
One idea could be exploring the origin of Lightbringer in more depth. Maybe it was created by an ancient civilization long before the events of 'Game of Thrones'. Another could be a story where a new character discovers Lightbringer and has to learn how to control its power without succumbing to its dark influence.
Definitely Tyrion Lannister. In a crossover with 'The Simpsons', he could bring his sharp wit and political acumen to Springfield. He'd probably outwit Mr. Burns in no time. His complex personality and ability to adapt would make for a very engaging character in such a crossover fanfiction.
I think Bran Stark could be very interesting too. As the Three - Eyed Raven, he has vast knowledge and powers. In a future fanfic, he could use his powers to foresee and prevent new disasters or to guide the future of Westeros in a more positive direction. However, his new powers might also make him a target for those who fear his influence.
I think Daenerys Targaryen would be really interesting. If she were reincarnated, she could use her past experiences to be an even more powerful and just ruler. She already had a complex journey in the original series, and reincarnation would add more depth to her character. She might be able to avoid some of the mistakes she made in her first life, like trusting the wrong people.
Stormbreaker itself could be considered a character in a sense. If it were to appear in the Game of Thrones world, it would be an object of great power. Many characters would vie for it. It could end up in the hands of someone like Daenerys, who already has a connection to powerful and magical things. This would make her even more of a dominant force in the story.
Well, Daenerys Targaryen is often a popular choice. Her dragons and her journey of reclaiming the Iron Throne can be easily adapted into crossovers. For example, if she were to cross into a world full of magic - users, how would she use her power? Also, Jaime Lannister is quite popular. His character arc from a seemingly villainous knight to a more complex figure can be explored in different settings. In a crossover with a historical setting, his knightly skills and code of honor (or lack thereof at times) would be very interesting to play with.
Daenerys Targaryen is often a popular choice. Since she had a strong connection with the Dothraki in the original series, fanfiction can explore more of her relationship with them. For example, stories could focus on her early days with the Dothraki and how she really won them over, beyond what was shown in the show.
Podrick Payne is often overlooked. He has a lot of potential in a fanfiction. He could be revealed to have a hidden talent for strategy, having learned from all the great knights he has served. And Bronn, while not completely ignored, could be further explored. He could find himself in a situation where he has to choose between his love for gold and loyalty to a cause that he actually believes in, like helping the common people of King's Landing.
A Skagosian outcast. He could have been banished from his tribe for some reason, like not following their brutal traditions. This character would be interesting as he would be an outsider even in his own land at first, and his journey to either regain his place or find a new one could be full of adventure and self - discovery.
Bran Stark could also be the main character. His new powers as the Three - Eyed Raven give him a whole new perspective. He could be the one to guide Westeros into a new era. He could use his knowledge of the past and his ability to see things that others can't to make decisions that would shape the future of the Seven Kingdoms.