Percy Jackson himself is obviously very popular. His powers over water and his heroic nature make him a central figure in many fight scenes.
Annabeth Chase is also quite popular. Her intelligence and combat skills, especially with her dagger, add a different dynamic to the fighting in fanfic. She can often come up with clever strategies during battles.
Nico di Angelo is another popular character in these fanfics. His control over the dead and shadow - traveling abilities offer a lot of room for creativity. Fanfic writers often give him new powers or expand on his existing ones, like making his control over the dead more powerful or adding new elements to his shadow - traveling. His brooding and mysterious nature also makes him an interesting character to write about in the context of powers.
Obviously Percy himself is very popular. Since it's a 'Percy Jackson Reacts' scenario, he's at the center of it all. Fans love to write about his reactions.
Annabeth is also a very popular choice. Her intelligence and her relationship with Percy are often explored in fanfics. Writers might create scenarios where she uses her smarts to solve complex problems or where her relationship with Percy is put to the test in new and interesting ways.
Well, in many Percy Jackson alternate universe fanfic, Leo Valdez is quite popular. People love to write about his inventions in different scenarios. Maybe he creates a super - powerful weapon that changes the balance of power between the demigods and the monsters. Grover also has his fans in these fics. He could be in a universe where he's the most powerful satyr ever and has to use his nature - related powers to save the world. And of course, Clarisse La Rue can be really interesting in alternate universes, like a Clarisse who teams up with her former enemies to fight a greater threat.
Hazel Levesque is often a popular character. Her ability to control the Mist and her connection to the Underworld make her a very interesting character to write about. She can bring a lot of mystery and power to a fanfic story.
Percy himself is obviously very popular. After all, it's his series. Annabeth is also a fan favorite, as her intelligence and strong will make for interesting storylines. Nico di Angelo is quite popular too, especially when his powers and his somewhat dark nature are explored in fanfiction.
One popular original character is often a new demigod with a unique power. For instance, a demigod who can control time on a small scale, which comes in handy during battles and tricky situations. They add a fresh element to the existing world of Percy Jackson.
Grover can be a key character too. In some 'Percy Jackson blind fanfic', Grover uses his empathy link with Percy in a unique way to assist him. His loyalty to Percy is further emphasized in these stories.
Percy is definitely one of the most popular. His powers and his relatable, humorous personality make him a natural choice for fanfiction. Annabeth is also very popular as she is intelligent and strong - willed. Her strategic thinking can add a lot of depth to the gaming - related stories.
Percy Jackson himself is still very popular. People love to write about his further adventures, his growth as a demigod, and his relationships. For example, his relationship with Annabeth might be explored in more depth, like how they deal with new challenges as a couple.