One idea could be that the RWBY characters are transported into the Overwatch universe and have to team up with the Overwatch heroes to fight a new common enemy, like a powerful omnic - Grimm hybrid. Another could be a friendly competition between the two groups in a series of combat trials to see who is more skilled.
One idea could be that Naruto is somehow transported to the Overwatch universe. He might mistake some of the heroes for ninjas at first. For example, Genji with his ninja - like appearance and skills. Naruto could try to form a team with the Overwatch heroes to fight a common enemy, like the Talon organization. He could teach them some of his ninja techniques in return for learning about their high - tech weapons and strategies.
Well, a cool concept for an Overwatch RWBY crossover fanfic would be to focus on the technology aspect. Overwatch has a lot of advanced tech, and RWBY has its own unique Dust - based technology. The fanfic could explore how the two types of technology interact. For instance, Mercy's healing staff could be affected by Dust in the RWBY world, or Torbjörn could use RWBY - style materials to upgrade his turrets. And of course, the character interactions would be great. Winston and Zwei could be an interesting pair to write about.
One idea could be that Goku accidentally travels to the RWBY universe during a sparring session that goes wrong with Whis. He could be mistaken for a powerful Grimm at first, causing chaos. Then, he teams up with Team RWBY to fight a new super - strong Grimm that threatens all of Remnant.
One idea could be the Overwatch heroes being transported to the RWBY world. They could team up with Team RWBY to fight a new common enemy, like a powerful Grimm that is immune to normal attacks but vulnerable to Overwatch tech. Another plot could involve a character exchange, where a RWBY character like Ruby goes to the Overwatch world and learns about their technology and fighting styles, and then brings back new knowledge to her own world.
One idea could be that the RWBY characters are transported to an alternate universe where they have to team up with Rooster Teeth's other original characters to fight a common enemy. Maybe a new type of Grimm that has some connection to a technology that Rooster Teeth characters are familiar with.
One idea could be the different combat styles of RWBY and STRQ teams clashing and then learning from each other. For example, Ruby's speed might be something the older STRQ members could be impressed by and give her some pointers based on their more experienced fighting. Another plot idea could be exploring the relationships between the characters from both groups. Maybe Weiss could form a bond with one of the STRQ members over their shared love for music, if that's part of their backstory. It could also involve a common enemy that forces them to work together and in the process, they discover secrets about their respective teams.
Reinhardt and Yang would be quite a pair. Reinhardt is the fearless crusader with his rocket - powered hammer and shield, while Yang is a brawler with her gauntlets. They could have some epic battles side by side, and Yang could learn about honor and chivalry from Reinhardt, while Reinhardt could be impressed by Yang's tenacity and determination in the face of danger.
One idea could be that Harry Potter and his friends accidentally get transported to the RWBY world. They could then use their magic in unique ways to help the RWBY characters fight Grimm. For example, Hermione could use her knowledge of spells to create new defenses against the Grimm that the RWBY characters haven't thought of before.
One idea could be a crossover where the RWBY characters are transported to a different Rooster Teeth universe and have to team up with the local heroes to defeat a common enemy. For example, they could end up in the world of 'Red vs Blue' and have to deal with the chaotic military situations there.
One idea could be exploring a new character's journey in the RWBY world. Maybe a character from a different kingdom who has unique abilities and must team up with the main RWBY characters to face a new threat. Another plot could involve time travel, where a character goes back in time to change a crucial event in RWBY's history. A third idea is a story focused on the Grimm's origin and how to potentially find a way to permanently stop their creation.