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.
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, 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.
In such a fanfiction, Naruto might take on a protective role. He could use his ninja skills to keep the toddler safe from any potential threats in the Naruto world, like rogue ninjas or dangerous beasts.
Well, Naruto finding a baby boy in a fanfiction could lead to all sorts of adventures. Maybe the baby has some special power or is a key to some mystery in the Naruto world. Naruto would then have to protect the baby from those who would want to use the baby's power for evil.
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.
Maybe Naruto discovers the violin and is instantly intrigued by its sound. He might try to learn how to play it, seeing it as a new form of self - expression. Since Naruto is known for his determination, he could struggle at first but then gradually master the instrument.
In the fanfiction, Naruto might take the puppy back to the village. He could name it something cute like 'Kiba Jr.' and train it to be a helpful ninja dog.
Well, Naruto might take the egg to his home and try to figure out what kind of creature is inside. Maybe he'd ask Kakashi for advice on how to take care of it.
The shrine could be a place of great significance related to the Nine - Tails. Maybe it has the ability to suppress or enhance the Nine - Tails' power within Naruto. This could lead to Naruto having to make some difficult decisions about whether to use this new - found power or keep it in check.
Well, Naruto could be on one of his adventures and suddenly come across a Pokegirl. He might be confused at first, not understanding what she is. Then, they could team up. Maybe the Pokegirl has some special powers that Naruto is interested in, and they go on a journey to fight some common enemy.