Well, when Naruto and Jiraiya's jutsu goes wrong, it could lead to a disruption in the space - time continuum within the fanfiction world. Jiraiya might be sent to a different dimension while Naruto is left behind, and they have to find a way to reunite. This could involve Naruto having to learn new jutsu to open a portal to the dimension Jiraiya is trapped in. It would be a long and arduous journey for Naruto, full of self - discovery and growth as he tries to save his mentor.
The story could develop with Naruto and Jiraiya having to face the consequences of their failed jutsu. Maybe they are shunned by the village at first because of the danger they pose.
A 'Solar - Flare Rasengan'. Naruto could combine his wind - style chakra with some kind of solar - based energy he discovers. This jutsu would be like a super - charged Rasengan that emits a blinding light as well as powerful wind - based damage.
There could be a jutsu that allows for instant teleportation across long distances. This jutsu might be a new discovery in the fanfiction world, perhaps created by a character who has been experimenting with space - time ninjutsu. They might use it to quickly get in and out of battles or reach far - off places in a blink.
It could be a new form of Rasengan. Maybe Naruto discovers a way to combine different elements with the Rasengan more effectively, like adding lightning to it for a more powerful and faster attack.
Jiraiya might comfort Naruto by sharing his own experiences. He could tell Naruto about the times he faced difficulties and how he overcame them. For example, he might talk about his training with the toads and how he grew stronger through perseverance.
There's also the 'Inferno Storm Jutsu' in some fanfictions. It creates a large - scale storm made entirely of fire. The fire in this storm has different intensities, with the center being the hottest and most destructive. It can cover a large area, making it a great offensive move against groups of enemies.
Maybe Sasuke. Although they are rivals, they also have a deep bond. Sasuke might have come across a unique jutsu during his travels and decide to teach it to Naruto so that they can both become stronger and better protect their village.
It could be Naruto himself who discovers and uses the Katon Hijingakure no Jutsu in the fanfiction. Since he's always exploring new jutsus and pushing his limits.
He might learn a time - traveling jutsu. This would be really cool as it could allow him to go back and change certain events in the Naruto world, or gain knowledge from the past to use in the present battles.