One idea could be that Naruto and his friends get transported to the RWBY world. They team up with Ruby and the gang to fight a common enemy that combines the threats from both universes, like a group of powerful ninja - Grimm hybrids.
Another plot could involve a character from RWBY traveling to the Naruto world and learning ninjutsu. They then bring those skills back to their own world and use them to fight the Grimm in new and unexpected ways. This could also lead to a cultural exchange between the two universes as the characters learn about each other's ways of life.
One idea could be that Naruto characters are transported to the RWBY world. Naruto, with his determination and never - give - up attitude, could inspire Ruby and her team. Maybe they team up to fight a common enemy like a powerful Grimm that has abilities similar to some of the Akatsuki members. Another plot could involve sharing of jutsu and semblances. For example, Sasuke could teach Blake some of his lightning - based jutsu and in return, Blake could show Sasuke how to better control his chakra flow using her semblance knowledge.
Another plot could involve a RWBY character ending up in the Naruto universe. Say, Weiss gets sent to Konoha. She might initially struggle with the different culture and the use of chakra, but eventually she could use her Glyphs in unique ways by combining them with chakra. This could also lead to some interesting interactions between her and the ninja students there.
One idea could be that Naruto characters are transported to the RWBY world. Naruto himself could befriend Ruby and they could learn from each other's combat styles. For example, Naruto's chakra control might inspire Ruby to better control her own energy. Another plot could involve the Akatsuki from Naruto being interested in the Dust in RWBY's world and causing chaos to obtain it.
In a 'Hunter x Hunter crossover RWBY fanfiction', it could be that the Nen abilities in Hunter x Hunter are seen as a form of magic in the RWBY world. Some of the RWBY characters are fascinated by this new power source and want to learn about it. So, they make a deal with the Hunters to exchange knowledge about their respective powers. This leads to some really interesting training sessions and battles where they combine Nen and Semblance powers.
Perhaps in this fanfiction, Weiss discovers a strange portal and steps through it, ending up in the Naruto world. She meets Naruto and is intrigued by his ninja abilities. They could start training together, with Weiss learning some ninja techniques and Naruto learning about Dust. Their combined skills could then be used to protect Konoha from a new threat that has some similarities to the Grimm from her world.
Perhaps there could be a situation where the Grimm from RWBY start to invade the world of Genlock. The Genlock team, with their diverse skills and abilities, would have to learn about the Grimm from the RWBY characters in order to fight them effectively. And in return, the RWBY characters could learn about Genlock's technology and combat strategies. For example, they could figure out how to use the Genlock's mech - like suits in their battles against the Grimm. It would be a great opportunity for character development as they interact and adapt to each other's ways.
One idea could be that Naruto and Ichigo meet in a dimension where their powers are combined. They have to fight a new, powerful enemy that threatens both their worlds. For example, a villain who can manipulate the energy of chakra and reiatsu at the same time.
One idea could be that Naruto, through some magical or mysterious event, ends up in a different universe where he has to deal with a harem of various characters from different anime. For example, he might find himself in a world with characters from Fairy Tail, One Piece, and Bleach all vying for his attention. Another could be that Naruto's already large group of friends in the Naruto universe start to develop romantic feelings for him all at once, creating a sort of accidental harem situation. Maybe Sakura realizes she always loved Naruto more than Sasuke, Ino also has a change of heart, and then some new female characters are introduced who also fall for him.
Well, a 'naruto x rwby fanfic' could center around a training arc. Imagine Naruto training the RWBY team. He could help Ruby improve her speed and combat skills by teaching her some of his ninja movement techniques. Yang could learn from Naruto how to better control her temper during battles, similar to how Naruto had to control his Nine - Tails' chakra. Meanwhile, the Naruto characters could also be learning about the Grimm and how to fight them. They could incorporate their ninja tools and jutsu to combat these new and strange enemies from the RWBY world.
One idea could be that the characters from RWBY are transported into the Destiny universe and have to learn to use the unique weapons and powers there. For example, Ruby could be fascinated by the Exotic weapons in Destiny and try to incorporate their technology into her Crescent Rose. Another plot could involve the Guardians from Destiny being sent to the RWBY world to help fight against the Grimm. They would have to adapt to the new environment and team up with the RWBY characters. The third idea is that a powerful enemy from the Destiny universe somehow crosses over to RWBY's world and the combined forces of both universes have to stop it.