Malcolm Merlyn is another good character for an Arrow fanfic. His motives are often ambiguous. He could be written as a more sympathetic character in a fanfic, or his past and his relationship with Thea could be delved into more deeply, adding new layers to his already complex character.
Oliver Queen is an obvious choice. He has such a complex backstory with his time on the island, his return to Starling City, and his evolution into the Green Arrow. His relationships with other characters like Diggle, Felicity, and Laurel also offer a lot of material for a fanfic.
Felicity Smoak is also great. Her character provides a contrast to Oliver's more brooding nature. She's smart, witty, and her growth from a tech - support girl to an integral part of Team Arrow can be explored in many interesting ways in a fanfic.
Xander is a great character to feature. He's always full of energy and getting into fun adventures, which can make for an exciting story. Also, Emma, as she's often the voice of reason among the campers and can bring a sense of stability to the plot. And Lou, the counselor, is another good choice as she has to deal with all the camper's antics.
Erina could also be great. Her refined palate and high standards add a layer of complexity. A fanfic could explore her journey of trying new and unorthodox cooking styles while still maintaining her elegance and grace in the kitchen.
Syd is a character that can bring some humor to a fanfic. His interactions with Kat and his role in the story can be expanded. He could be involved in some comical misadventures while also being an important part of the group.
In my opinion, Bergy is an underrated character who could shine in a fanfic. He has that nerdy charm and his technical skills could be put to great use in a story. Maybe he discovers a glitch that is related to his area of expertise and he has to take the lead in fixing it. Miko and Five are also obvious choices. Miko's enthusiasm and Five's cool - headedness can create a great dynamic. They could be on a mission to stop a glitch that is spreading across all the arcades in town and along the way, they have to overcome their own personal differences as well as the challenges posed by the glitch.
I think Megumi would be a wonderful character to feature. She has a lot of growth potential in a fanfic. Starting from her insecurities and seeing her develop into a more confident cook. Also, Kuga can bring in an element of exotic and bold cooking styles. And don't forget about Akira, who has his own brand of precision cooking. Including these characters can add different flavors to the fanfic, both literally and figuratively.
In my opinion, the best characters to feature in a Naruto Pokemon fanfic would be Naruto, Sakura, and Shikamaru. Naruto is obvious as he's the main character and his never - give - up attitude can inspire his Pokemon. Sakura has the medical skills which could be useful in treating injured Pokemon. Shikamaru is super intelligent and could come up with great strategies for Pokemon battles. They could all have different types of Pokemon that complement their personalities, like Naruto with a Fire - type Pokemon, Sakura with a Grass - type for her healing abilities, and Shikamaru with a Psychic - type to match his intelligence.
Naruto, of course, is a must - feature character. He's the main character of the Naruto series and his addition to a story involving Susanoo would bring a lot of interesting dynamics. Sasuke is also a great choice as he is an Uchiha and has a natural connection to Susanoo. Another good character could be Kakashi. He has experience with different powers and could be a mentor - like figure in a fanfic about Naruto and Susanoo.
Oz Vessalius is a great character to feature. His complex backstory, including his connection to the Abyss, gives a lot of room for exploration in a fanfic. Another good one is Alice. Her brash and often unpredictable nature can add a lot of interesting twists to a story. Also, Gilbert is a character full of loyalty and internal conflict, which can be used to create engaging storylines.
Kakashi would be an interesting character to include. His intelligence and combat experience could make for an exciting story as he figures out how to best utilize the shield in different scenarios.
Sasuke is an obvious choice. He's already associated with swords like the Kusanagi. A fanfic could explore his further development with the sword, perhaps unlocking new abilities or techniques.