Well, if Naruto finds a gun in a fanfic, he might see it as a threat to his village. So, he would probably take it to someone like Kakashi. Kakashi, being more worldly, would recognize it as a dangerous foreign weapon. They might then try to find out where it came from and who brought it into the ninja world, leading to a whole mystery - solving adventure in the fanfic.
In such a fanfic, Naruto could also be in a situation where he's forced to use the gun. Maybe he's in a place where his normal ninja skills are useless. He might be hesitant at first because it's not his usual way of fighting. But if his friends are in danger, he could pick it up and use it in a very Naruto - style way, like using his quick reflexes to dodge enemy attacks while trying to figure out how to aim and fire the gun effectively.
In a 'Naruto finds a gun' fanfic, one possibility is that Naruto, being curious, might initially mistake it for some strange new weapon from another land. He could try to figure out how it works in his own Naruto - like way, perhaps by trying to infuse chakra into it, which might lead to unexpected and comical results, like the gun shooting out chakra - blasts instead of bullets.
Well, it depends on the context of the fanfiction. If it's set in a more modern - ish Naruto world, perhaps Naruto would see the machine gun as a new and powerful tool. He might take it to his friends at Konoha to study it together. Sakura, being the intelligent one, could try to analyze it while Naruto is eager to test its power against some powerful foes. However, this would also bring up questions about the balance of power in the Naruto universe.
Well, if Naruto finds a gun in a fanfiction, it would be really out of place in the ninja world he's from. But he might be confused at first. He'd probably try to figure out what this strange object is, since it's so different from his shurikens and kunai. He might even accidentally set it off, causing chaos in the village.
Well, he might discover a hidden jutsu scroll in the library. It could be a long - lost technique that gives him an edge in battles.
The story in the 'naruto finds a tank fanfic' could also take a more comical turn. Naruto could accidentally set off some alarm on the tank and then start panicking, thinking it's about to attack him. Or he might mistake the tank for a really big and strange animal and start trying to communicate with it in his own Naruto - like way, which would be really funny to read.
In the 'Naruto finds an egg fanfic', Naruto may take the egg to his teacher, like Iruka. They might study it together. It could be an egg of a rare creature. Naruto's sense of adventure would lead him to discover more about the egg, and perhaps it will hatch into a cool animal that becomes his new friend or ally.
He could find the sword in an ancient tomb. This tomb might be filled with traps and puzzles that Naruto has to overcome. Once he gets the sword, he discovers that it glows when near an enemy's weak point. So, he starts using this ability to his advantage in battles.
Well, he might be initially confused. Naruto comes from a world with ninjas, not a modern army base. He could think it's some new kind of enemy stronghold. Maybe he'd try to infiltrate it in his typical ninja way, using stealth and jutsus.
In a fanfic where Naruto finds an army base, he might initially be on high alert. He could use his ninja skills to scout the area stealthily. Maybe he would try to figure out if the army base is a threat to his village. If the people in the base seem hostile, he would likely be ready to defend himself using his jutsus like the Rasengan.
Maybe Naruto discovers that the weird artifact has some special powers, like the ability to open portals to other dimensions.
In the fanfiction, Naruto could meet someone who knows a lot about the Kusanagi. This person could be an old sage or a mysterious traveler. They could teach Naruto how to use the sword properly and unlock its true potential. It could also lead to Naruto getting into some battles where the Kusanagi gives him an edge, and he has to learn to adapt his fighting style to include swordplay.