One interesting crossover could be the combination of TF2's unique character classes with Overwatch's diverse heroes. For example, the Scout from TF2 could have a race against Tracer from Overwatch. Another could be the Medic from TF2 teaming up with Mercy from Overwatch to heal a group of both TF2 and Overwatch characters in a chaotic battle scenario. Also, the Engineer from TF2 might build structures in an Overwatch - like map to help both teams' forces.
First, you need to understand the characters from both TF2 and Overwatch well. Know their personalities, abilities, and backstories. Then, come up with an interesting plot that can involve both sets of characters in a meaningful way. For example, a threat that only they can defeat together. Also, don't forget about the unique humor in TF2 and the more serious tone in some parts of Overwatch. Try to blend them well.
Another theme is the exploration of different game mechanics. Writers often play with the idea of how the TF2's class - based system and Overwatch's hero - based system could coexist or clash in a fanfic story. It can lead to really interesting scenarios and battles. And also, the theme of teamwork or lack thereof between the two groups is often explored. Since both games have elements of teamwork, seeing how the characters from different games work together or against each other is quite fascinating in fanfics.
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 possibility is that there's a rift in time or space that brings the two universes together. The TF2 and Overwatch characters find themselves in a strange new world that's a mix of both of their own. They have to figure out how to get back to their respective universes while also dealing with local threats. Some characters might be tempted by the different cultures and powers they encounter, which could cause internal conflicts within the combined group.
One great TF2 and Overwatch fanfic is 'The Mercs and the Heroes' which combines the unique characters from both universes in an action - packed adventure. It has interesting crossovers and character interactions.
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.
Social media platforms can be useful too. On Twitter or Tumblr, there are groups and hashtags related to TF2 and Overwatch fanfiction. By following these hashtags or joining relevant groups, you can discover new fanfictions shared by other fans. Additionally, some fanfiction authors promote their work on these platforms, so you might find some hidden gems.
Mercy from Overwatch and the Medic from TF2 would be likely allies. They both have a strong focus on healing. Mercy's ability to fly and revive teammates could be well - complemented by the Medic's Ubercharge ability. Another pair could be Tracer and Scout. They are both fast - moving characters. They could use their speed to scout out areas, steal intel or make quick strikes against the enemy.