Perhaps Percy sacrifices himself to close a portal to the Underworld that is spilling out monsters and chaos. He realizes that his life force is the key to shutting it down, so he willingly gives himself up. He could say some heroic last words to his friends, like 'Tell Annabeth I love her' before disappearing into the portal.
One possibility is that Percy sacrifices himself to save his friends and Camp Half - Blood from a powerful, unbeatable enemy like an ancient primordial god. He might use his powers to create a shield or diversion that allows everyone else to escape while he faces certain death.
Perhaps in the fanfic, there is a prophecy that states only a hero's ultimate sacrifice can save Artemis from a dark curse. Percy, being the selfless hero he is, decides it has to be him. He goes through a series of trials first, trying to find an alternative way but in the end, he has no choice. He sacrifices his life force to break the curse on Artemis. This act not only frees Artemis but also has far - reaching consequences in the Percy Jackson universe, like changing the power dynamics between the gods and demigods.
One possible plot could be that Percy is overwhelmed by the pressure of his demigod duties. He has constantly faced life - threatening situations, seen friends die, and felt the weight of the prophecy on his shoulders. In this fanfic, he might see shooting himself as a way to end the cycle of pain and danger for himself and those he loves.
Well, it could be that Naruto sacrifices himself to seal away a dark and ancient curse that is threatening to destroy not only the ninja world but all of existence. He realizes that his unique connection to the tailed beasts and his strong willpower make him the only one who can perform this self - sacrificing sealing jutsu. So, he says his goodbyes to his friends, family, and the village he loves and gives up his life to save everyone.
In the fanfic, it could be that Fleur is in a situation where she has to perform a dangerous task to save the wizarding world, like going into an ancient and deadly magical place. Harry, realizing the importance of her mission and also having deep feelings for her (maybe a secret love), sacrifices his own safety by going with her and ultimately giving his life to ensure she can complete the task and save everyone.
One scenario could be that they are facing a powerful monster. The monster is about to strike Annabeth, and Percy jumps in front of her at the last moment, taking the fatal blow. Another possibility is that they are in a dangerous situation like a collapsing building or a sinking ship, and Percy uses his powers to ensure Annabeth's escape while he stays behind and perishes.
I'm sorry I can't directly recommend a specific 'Percy sacrifices himself for Artemis' fanfic. But you can try searching on fanfic platforms like Archive of Our Own (AO3). There are tons of fanfics there, and by using relevant keywords in the search bar, you might be able to find one that suits your interest.
One possible plot could be that Percy wakes up in the mental hospital with no memory of how he got there. He starts to notice strange things like the nurses and doctors seem to have an otherworldly aura. As he tries to regain his memory, he discovers that the hospital is a front for some sort of mythological experiment. He then teams up with other demigods who are also trapped there to escape and expose the truth.
One possible plot could be that in a final battle against an extremely powerful enemy, Naruto realizes that the only way to save Hinata and the entire village is by using a forbidden jutsu that will cost him his life. He makes this sacrifice with a smile on his face, knowing that Hinata and the others will be safe. Hinata is heartbroken but also determined to carry on Naruto's legacy of protecting the village.
In such a fanfiction, one possible plot could be that Naruto faces an extremely powerful enemy who is about to kill Kakashi. Naruto, being the selfless hero he is, steps in and uses a powerful jutsu that requires sacrificing his own life to save Kakashi. This could lead to a great deal of mourning among the other characters, especially those close to Naruto like Sasuke and Sakura. They might then vow to carry on Naruto's will and protect the village even more fiercely in his memory.
Well, in such a fanfic, perhaps Percy ends up in a new camp or place full of demigods he doesn't know. He has to prove himself without his mom's support. He could befriend some unlikely characters who help him understand more about his mother's disappearance. And in the end, he might find that his mom left to protect him from a greater threat that he now has to face on his own.