A fun fanfiction idea could involve a friendly competition between the two groups. Like a series of challenges that test both the combat skills and the unique abilities of each team. This would allow for a lot of humorous moments as well as some intense action scenes as they compete against one another.
Another interesting concept could be a crossover in which the technology from TF2 is integrated into the Overwatch universe, or vice versa. For example, the Medic's healing technology being used to enhance the Overwatch medics' abilities. This could lead to some really cool character interactions and story developments as they learn to work with new equipment and each other.
A great concept could be a crossover tournament. The two teams, TF2 and Overwatch, compete in a series of challenges. These challenges could include things like a sniper - only round where Widowmaker from Overwatch and Sniper from TF2 go head - to - head. Or a melee combat round with Reinhardt and the Demoman. It would be a chance to explore the different abilities and personalities of the characters in a competitive setting.
A more complex plot could involve a mysterious force that is causing glitches in both worlds. Some characters from Overwatch and TF2 have to work together to figure out the source of this force. For example, Tracer from Overwatch and Scout from TF2 could use their speed to scout out the affected areas while their respective teams of engineers, like Torbjörn and Engineer from TF2, try to fix the glitches in the technology.
One idea could be an Overwatch crossover with the Star Wars universe. Imagine Tracer using her time - traveling abilities in the middle of a lightsaber duel. Another could be a crossover with the Harry Potter world, like Pharah flying on her rocket launcher over Hogwarts. And a crossover with the Marvel universe, where Reinhardt teams up with Thor to fight some powerful villains.
A crossover with a cyberpunk - themed story could be really cool. Genji's cybernetic enhancements would fit right in. He could be on a mission in a dystopian city, facing off against powerful corporations and their enforcers. Along the way, he might meet new allies who are also fighting for justice in this harsh environment.
Another concept could be a story where a character from Halo, say Master Chief, gets transported to the Overwatch universe. He has to adapt to the different rules and powers there while trying to find a way back home. Along the way, he could form unexpected alliances with Overwatch heroes and learn about their world, and they could learn from his military discipline and combat experience.
Maybe the villains from BNHA team up with some of the evil forces in the Overwatch world. Then the combined good guys, including both BNHA heroes and Overwatch agents, have to figure out how to defeat this new, dangerous alliance. It could lead to some really cool battles and character interactions, like All Might facing off against Doomfist.
One interesting idea could be an Overwatch crossover with the world of Harry Potter. For example, Tracer could be a student at Hogwarts, using her time - traveling abilities in magical ways within the school. Another idea is a crossover with the Star Wars universe. Maybe Reinhardt as a Jedi, with his rocket hammer being a unique lightsaber - like weapon. And a crossover with the Lord of the Rings, where Orisa could be a guardian of a certain part of Middle - earth, protecting it from the forces of evil with her shield and gun.
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 interesting TF2 Overwatch fanfiction could be about a crossover battle where the characters from both universes accidentally meet in a strange dimension and have to fight together against a new, unknown threat. For example, the Engineer from TF2 and Torbjorn from Overwatch might team up to build some amazing defenses.
Another interesting concept could be a character swap. Imagine Tracer from Overwatch in the Halo universe, using her time - jumping abilities in the middle of a large - scale Halo battle. Or a Spartan in the Overwatch world, trying to adapt to the more urban and team - based combat scenarios there.