Well, it could be about Naruto having some sort of connection to the Titans. Maybe he inherits some Titan powers and has to use them in the Naruto world. He might face challenges from both the Naruto villains and those related to the Titan world, like having to fight against those who want to control his newfound Titan abilities.
Another possible antagonist could be a rogue Titan from the Titan world who somehow makes its way into the Naruto universe. This Titan could be enraged or corrupted and see Naruto as an enemy because of his mixed heritage. It could cause destruction across the ninja world, and Naruto would have to stop it using his ninja skills and Titan powers.
In many fanfictions, Percy being the son of a Titan can lead to some really interesting storylines. It might change his relationships with the Olympians. For example, he could be seen as a threat by some, or as a potential ally by others who want to use his Titan heritage for their own purposes. His powers could also be different or enhanced, perhaps having more control over primordial elements related to Titans.
If Naruto was an Armored Titan in a fanfiction, he'd be a force to be reckoned with. His speed and agility as a ninja would likely transfer to the Titan form, making the Armored Titan much more mobile. He could also use his Rasengan in the Titan form, maybe by concentrating chakra into the Titan's fist.
One idea could be that Naruto somehow gets transported to the world of Attack on Titan and gains the power of the Armored Titan. He might use his ninja skills in combination with the Titan's strength. For example, his shadow clone jutsu could be used to create distractions while the Armored Titan attacks enemies head - on.
In this fanfiction, Percy's role in the prophecy could change. Instead of being the hero for the Olympians, he could be the one to bring a new order with his Titan powers. His connection to Poseidon would be strained or even broken. He would have to find new allies, perhaps among the other demigods who are also outcasts because of their different heritages. And his battles would be against different foes, not just the Titans' old enemies but also those who oppose the idea of a demigod with Titan blood.
One common theme is identity. Since Percy is the son of a titan, he has to figure out who he really is and where he belongs. Another theme is power. With his new heritage, he often has to learn to control new powers.
Well, there's 'Titan - Shinobi Alliance'. This one is quite interesting as it imagines a scenario where the characters from Naruto and Attack on Titan form an alliance. The story has some great action scenes where ninjas and the Survey Corps work together. It also explores the cultural differences between the two groups, which makes for a very engaging read.
Well, I've seen a few. They usually take Naruto's ninja abilities and combine them with the Titan - shifting powers in interesting ways. For example, Naruto might use his shadow clones while in Titan form. However, the quality can vary a lot. Some are really well - written with detailed character development and exciting plots, while others might be a bit lacking. So it takes some time to find the good ones.
One possible scenario could be Naruto using his godlike powers to quickly assess and counter the Titans. His ability to sense danger and move at high speeds would make him a formidable force against the Titans. For example, he could use his shadow clones to distract the Titans while he goes for the kill with a Rasengan.