One interesting 'naruto heartless fanfiction' could be where Naruto loses his emotions due to a dark jutsu. In this story, he becomes a super efficient ninja but at the cost of his humanity. His friends struggle to bring back the old Naruto.
In some 'naruto heartless fanfiction', Naruto could be cursed by an ancient power that strips him of his heart. As a result, he doesn't feel pain, love or remorse. This makes him a feared figure in the ninja world. His sensei Kakashi tries to find a way to break the curse but it's not easy as the power is very mysterious.
One interesting concept could be how the heartless bloodline affects the character's relationships. For example, it might make them more isolated as others fear their power. Another concept could be the unique jutsu or abilities that come with this bloodline. It might allow for some really cool and unusual combat techniques that set the character apart from others in the Naruto universe.
In some fanfictions, the heartless god could be from another dimension and has come to the Naruto world seeking something. This could set off a chain of events where the characters need to figure out the god's motives and stop it from achieving its goals. It might also introduce new types of jutsu or powers that are unique to this 'heartless god' and the dimension it comes from.
Perhaps a dark power corrupts him. In the fanfiction, there could be some sort of dark chakra or evil entity that latches onto Naruto. This entity could slowly eat away at his emotions, starting with his heart, making him gradually lose his ability to feel empathy and turn heartless.
Well, in some fanfictions, Naruto might control the heartless through his strong will and the power of his chakra. Maybe he uses some new jutsu he developed specifically for this purpose.
In a 'heartless' fanfiction based on a superhero story like Batman, the Joker could be made even more heartless. Instead of his usual chaotic yet somewhat understandable motives, he could be written to have no redeeming qualities at all. He might be shown as someone who enjoys pure destruction without any purpose other than to cause pain. This can add a new and darker dimension to the story.
One interesting Naruto fanfiction could be those that explore an alternate universe where Naruto becomes a villain. It flips the whole story on its head and shows a different side of the characters. Another type is the ones that focus on Naruto's relationships in a more in - depth way, like his friendship with Sasuke evolving in unexpected ways.
One interesting Naruto fanfiction could be about Naruto learning a new and extremely powerful jutsu from an ancient scroll he discovers. This jutsu gives him an edge in battles against powerful foes like Madara. Another could be a story where Naruto travels to a different dimension and has to team up with alternate versions of his friends to save both worlds.
One interesting Naruto fanfiction could be about Naruto having a secret power that he discovers during a mission in a hidden land. This power could change the way he approaches battles and his relationships with his friends.
Some fanfictions in 2017 could focus on Naruto's family life. For example, how he is raising his children and passing on his skills and values. It could show a more domestic side of the great hero.
One interesting Naruto fanfiction could be about Naruto learning a new and unique jutsu from an ancient scroll. Another might be a story where Naruto and Sasuke have to team up against a completely new and powerful enemy that doesn't exist in the original series. There are also fanfictions that explore what would happen if Naruto was raised in a different village.