One idea could be a crossover with the Alien franchise. Picture Isaac Clarke in a derelict Alien ship, facing both Necromorphs and Xenomorphs. The different types of terrifying creatures could create a really intense and unique horror scenario.
Another interesting concept is a crossover with the Doom series. The Doom Slayer could end up in the Dead Space universe. He would be this unstoppable force against the Necromorphs, and his brutal combat style would contrast with Isaac's more methodical approach. It would be an action - packed fanfiction with lots of gore and epic battles.
A Dead Space and Mass Effect crossover would also be cool. Maybe the crew of the Normandy stumbles upon a Dead Space - like situation. Shepard would have to use his combat skills and leadership to deal with the Necromorph threat, while also trying to figure out the mystery behind their existence in the Mass Effect universe.
You could do a crossover with 'Castlevania'. The gothic horror elements of 'Castlevania' would blend well. Dracula could be a powerful killer, and the heroes from 'Castlevania' could be survivors. The survivors might have new abilities like using holy water or magic spells against the killers. It would also be interesting to see how the 'Dead by Daylight' maps would be transformed with the addition of 'Castlevania' - like architecture and elements.
One idea could be a story where characters from 'Dead or Alive' cross over into a post - apocalyptic world. They could use their fighting skills to survive against new and dangerous enemies. Another idea is a crossover with a fantasy realm, and the 'Dead or Alive' characters have to adapt to magic and mythical creatures. For example, Kasumi might learn to use magic spells while still relying on her ninja skills.
A cool 'Walking Dead Crossover Fanfiction' idea is to cross it with 'The X - Files'. Mulder and Scully could be investigating the zombie outbreak. They might find out that it's not just a normal virus but some kind of government experiment gone wrong, which ties in with the conspiracy theories they usually deal with. And the characters from 'The Walking Dead' would be skeptical at first but then realize they need Mulder and Scully's help to figure out the real cause of the zombies.
One idea could be a crossover with Resident Evil. The main character from Dead Rising could find themselves in a Resident Evil - like scenario, dealing with different types of zombies and bioterror threats. They could team up with Resident Evil characters like Leon or Claire to fight against a common enemy.
A cool 'fear the walking dead crossover fanfiction' idea would be a crossover with 'Stranger Things'. The Upside Down could be connected to the zombie outbreak in some way. The kids from Hawkins could team up with the survivors of 'Fear the Walking Dead' to fight both the zombies and the strange creatures from the Upside Down. It would be interesting to see how their different skills and knowledge would work together.
Well, a cool crossover fanfiction idea could be with 'The Witcher'. Geralt could find himself in the world of Red Dead Redemption, hunting monsters in the American frontier. Or, for a more comical crossover, think about a crossover with 'SpongeBob SquarePants'. SpongeBob and Patrick end up in the wild west and their naivete causes all sorts of chaos among the outlaws. Also, a crossover with 'Harry Potter' could be interesting, with wizards and witches showing up in the world of Red Dead Redemption and causing a stir with their magic.
One idea could be that the Winchesters somehow end up in the world of The Walking Dead. They might use their hunting skills to fight the walkers in a different way than the survivors are used to. Maybe they try to find a supernatural cause behind the zombie apocalypse.
One idea could be a crossover with a post - apocalyptic zombie series. The characters from Left for Dead could find themselves in a different zombie - infested world and have to adapt to new threats and survivors. For example, they might encounter a group that has a very different approach to survival, like a religious cult that believes the zombies are a form of divine punishment. This could lead to conflicts and alliances as the Left for Dead characters try to find their way back to their own world.
One interesting concept could be the combination of the Flood from Halo and the Necromorphs from Dead Space. Imagine how the two different types of parasitic, body - transforming threats would interact. Another concept might be the technology exchange. For example, how would the UNSC weapons and armor function in the Dead Space universe, and vice versa with the Dead Space engineering and weaponry in the Halo universe.
One idea could be a crossover with 'Rick and Morty'. Gary could team up with Rick and they'd have some wild adventures across different dimensions. Maybe they'd encounter some new alien species together that are a combination of the creatures from both shows.