A great fanfic often has well - developed characters. It should stay true to the personalities of Archer Emiya and Arturia as we know them from the original work. For example, Archer's stoicism and Arturia's sense of honor should be maintained.
Love and friendship is also a common theme. Some fanfics explore a romantic relationship between them, while others focus on a deep platonic friendship. Their bond can be a source of strength in the face of difficult challenges, and seeing how their relationship develops over the course of the story, whether it be love or friendship, is always interesting.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfics related to various fandoms, including those of Archer Emiya and Arturia. Just use the search function and type in their names. Another option is FanFiction.net, though the quality can vary more there.
One interesting fanfic could be where they team up on a quest. In this kind of story, Archer Emiya's combat skills combined with Arturia's leadership and noble ideals make for an exciting adventure. They might face a powerful enemy that neither could defeat alone, but together, they find a way to overcome it, leading to a deepening of their understanding and respect for each other.
Well, in such a fanfic, perhaps Archer sacrifices his arm while saving Arturia from a great danger. Maybe it could be a powerful enemy attack and Archer jumps in the way, taking the brunt of it on his arm to protect Arturia. This would be a very heroic and selfless act on Archer's part.
One possible plot could be that Irisviel summons Archer Shirou in a world where Arturia already exists. Maybe Irisviel has a specific plan to use Archer's abilities to help Arturia in some great battle or quest. Archer might initially be reluctant to work with Arturia due to their past differences, but as the story progresses, they start to understand each other better and form a strong alliance.
One great Archer Arturia Fate Night fanfic is 'The Bonds Beyond Time'. It delves deep into the relationship between Archer and Arturia. It shows how their fates are intertwined in different timelines. The story is filled with action-packed battles and emotional moments. The author's writing style is really engaging, making it a must - read for Fate Night fans.
It could be that Archer's loss of an arm makes him more determined. He might start to train harder with his remaining abilities, and in the process, discover new skills. This could also make him more respected among his comrades. Arturia, on the other hand, might start to see Archer in a new light, not just as a fellow fighter but as someone she deeply cares about on an emotional level.
A fanfic might explore the emotional journey when Arthuria summons Archer Emiya. Arthuria, having carried so much burden alone, might initially be hesitant to trust Emiya. However, Emiya's no - nonsense attitude and his own experiences of fighting for justice start to chip away at Arthuria's guardedness. They could bond over their shared sense of duty and form an unbreakable alliance in the face of powerful enemies.
A good Archer EMIYA fanfic often has a deep exploration of his character. Since he has a complex past and a rather cynical view of things, fanfics that dig into that are great. For example, those that show his internal conflict between his past self and the heroic spirit he has become.