Naruto is often involved as he is the main character of the series. His actions and adventures are central to most fanfictions, so if there's a heart attack situation, it's likely to somehow be related to him. For instance, he might be the one experiencing the heart attack or trying to save someone who has one.
Luna Lovegood could be a main character as well. Given her unique perspective on the wizarding world, she might have an unexpected way of dealing with Dementors. Maybe she can communicate with some otherworldly creatures that are natural enemies of Dementors and enlist their help during an attack.
Naruto himself is often a central character in 'naruto destruction fanfiction'. Since he is the main protagonist of the original series, fanfiction writers like to put him in situations where he has to deal with destruction. Sasuke is also frequently involved as his rival, and their relationship can be explored in the context of destruction, like if they have to work together to stop a greater threat of destruction.
Well, Naruto is obviously a main character in most of these. But there could also be Sasuke. He might be either an ally or an adversary in relation to the dagger. For example, if the dagger has a power that can either be used for good or evil, Sasuke could be tempted by its darker potential.
Some fanfictions might also include characters like Kakashi in important roles. As Naruto's former teacher, he could be a guiding figure or someone who has to adapt to Naruto's new level of power. He might also be involved in trying to keep Naruto's power in check if it starts to have negative effects on the ninja world.
Naruto himself is often a main character in naruto helmet fanfiction. Since he is the protagonist of the original series, it makes sense that he would be involved with a special helmet in fan - created stories. He could discover the helmet's powers and use them to become even stronger.
Naruto himself is often involved. Since he's the main character of the original series, in fanfiction with loopholes, he might use some loophole to achieve his goal of becoming Hokage faster or getting stronger in a unique way. Sasuke could also be a main character in such fanfictions. He might find a loophole to deal with his quest for revenge or his power - seeking in a different manner.
In many Naruto scream fanfiction, Kakashi Sensei can also play an important role. He might be trying to teach Naruto how to control his scream in a more strategic way, or he could be using Naruto's scream as a signal during a mission. Also, characters like Jiraiya might be involved. Jiraiya could be training Naruto to use his scream as a form of attack or defense, as part of some new and unique jutsu.
Definitely Naruto as the victim of hypothermia. Shikamaru could also be involved. He might be the one strategizing the rescue mission, using his intelligence to figure out where Naruto could be in the cold environment. And Hinata might be there too, her concern for Naruto adding an emotional aspect to the story.
Obviously Naruto himself is a main character. He is the one with the pacemaker so he is central to the story. Sasuke might also be involved. He could be initially skeptical of Naruto's new situation with the pacemaker but then come around to help. Sakura too, as a medical ninja, she could play a crucial role in understanding and perhaps even trying to modify the pacemaker.
Naruto is almost always a main character in 'naruto dice fanfiction' as the story is based on the Naruto universe. His friends like Sasuke and Sakura also often appear. Sasuke's cool and brooding nature can add an interesting dynamic when combined with Naruto's more upbeat and impulsive personality in stories related to the dice.