There's a fanfiction called 'Male Merida: The Archer Prince'. In this one, Male Merida is portrayed as a prince with extraordinary archery skills. He has to deal with political intrigue in the kingdom while also facing off against a dark sorcerer. It has an interesting plot and engaging characters.
The uniqueness also lies in the way it can rework the relationships. Instead of the mother - daughter dynamic in the original, there could be father - son or other types of relationships. In one fanfiction I read, Male Merida had a really interesting bond with his father that was different from what we saw in the movie. It added a new layer of depth to the story.
One common theme could be adventure. Since both Hiccup and Merida are known for their adventurous spirits in their respective movies. They might go on quests together in the fanfiction.
A frequently used trope is 'Injury/Healing'. For example, the reader could get injured and Male Merida takes care of them, which deepens their bond. Also, the 'Fish Out of Water' trope can be seen, like if the reader is from a different world or culture and Male Merida helps them adapt. This creates interesting situations and character dynamics. There's also the 'Love Triangle' trope sometimes, where another character might be vying for the reader's or Male Merida's affection, adding some drama to the story.
Fem Hiccup's more introverted nature might be a contrast to Male Merida's extroverted and brash personality. Hiccup might be hesitant to engage in some of Merida's wilder adventures at first. However, Merida's enthusiasm could draw Hiccup out of her shell. And Hiccup's calmness in the face of danger could help Merida learn to control his impulses a bit better. They would have an interesting dynamic where they learn from each other's strengths and weaknesses.
Another fanfiction could start with Merida getting lost in the Viking lands. Hiccup finds her and at first, they have a bit of a misunderstanding because of their different cultures. But as they spend time together, Hiccup helps Merida understand the ways of the Vikings and Merida teaches Hiccup some of her own skills, like how to better track in the forest. Eventually, they become good friends and help each other out in various adventures in the Viking world.
Another option is to check out Tumblr. There are often fanfiction communities and blogs dedicated to sharing and discussing different fanfictions. You might be able to find some Fem Hiccup x Male Merida fanfictions there, or at least get some leads from the community.
One possible plotline could be that Fem Hiccup and Male Merida meet in a forest while on their respective adventures. They initially clash due to their different ways of doing things. Hiccup is more methodical and Merida is more impulsive. But as they face a common enemy, like a giant magical beast, they learn to work together. Hiccup uses her engineering skills to create traps and Merida uses his archery skills to lead the beast into the traps. In the end, they become good friends and respect each other's cultures and abilities.
It's completely unacceptable. These characters are iconic and beloved in a general family - centered context. Fanfiction should be more about exploring positive aspects of the characters' personalities, their relationships in a non - sexual way, like their friendship or adventures together. Sexualizing them is disrespectful to the source material and the fans who enjoy the characters in their original form.
Some social media platforms like Tumblr can also be a source. There are often bloggers who are into fanfiction and might post or reblog stories about Merida and Young Macintosh. However, the search on Tumblr can be a bit tricky as it's not as organized as the dedicated fanfiction sites.