A good crossover idea is that the Akatsuki from Naruto are interested in the technology that Future Trunks has. They might try to steal it for their own purposes. This could lead to a series of battles and alliances. Also, since both Future Trunks and Naruto have a strong sense of justice, they could start a movement in both worlds to promote peace and cooperation between different races and species.
A crossover with the Star Wars universe would be cool. Future Trunks could find himself on a planet in the Star Wars galaxy. Maybe he has to help the Jedi fight against the Sith. His superhuman strength and ki blasts would be a new and powerful element in the Star Wars battles. He could learn about the Force while also teaching the Jedi about ki energy.
One idea could be a crossover with the Dragon Ball Super universe where Future Trunks teams up with Goku Black from an alternate timeline. They could be forced to work together against a new, powerful enemy that threatens both their timelines. Another plot could involve a crossover with the Naruto universe. Future Trunks could end up in the Hidden Leaf Village and learn about chakra. He might then combine his ki powers with some ninja techniques to fight a common foe. A third idea is a crossover with the One Piece world. Future Trunks could land on the Grand Line and join forces with the Straw Hat Pirates. They would have to face off against the Marines and other pirates while also trying to find a way for Trunks to get back to his own world.
A good 'Best Future Trunks Crossover Fanfiction' should first and foremost stay true to Trunks' character. His determination, his sense of justice, and his complex relationship with his timeline are all important aspects to maintain. For example, if he's crossed over into a different universe, his reactions to the new environment should be in line with what we know of his personality.
In a fanfic like this, the cultural clash would be interesting. Future Trunks comes from a world of high - tech and space travel, while the Fire Emblem world has its own medieval - like setting with magic and knights. He could introduce new ways of fighting and thinking to the Fire Emblem characters. For example, his knowledge of energy blasts might inspire some mages to try and develop similar attacks using magic. And the Fire Emblem characters could teach him about the use of magic and the importance of strategy in battles, which is different from his more straightforward combat style in his own world.
Perhaps a plot where Future Gohan and Future Trunks accidentally travel to an alternate timeline. There, they have to team up with different versions of themselves to defeat a common enemy. This would involve exploring how they interact with these alternate selves and how they adapt to the new environment and challenges.
One great 'Best Future Trunks Crossover Fanfiction' is 'Trunks and the Multiverse Adventure'. In this fic, Trunks travels across different universes and teams up with various versions of the Z - fighters. It has an exciting plot with lots of action and character development.
Gohan would be a great character to pair with Future Trunks in a crossover fanfic. Their friendship and combined power could make for an interesting dynamic. In a crossover, they could support each other in a new and unfamiliar world. Another good option is Vegeta. Since Future Trunks is his son, their relationship could be explored further in a different setting. They could also team up to fight stronger enemies. Also, Bulma could be paired with Future Trunks. She could use her scientific knowledge to help them in a crossover situation, like building new gadgets or finding a way home.
One idea could be Trunks traveling to an alternate universe where the rules of DBZ are slightly different. For example, the Saiyans never lost their planet but have a different culture. Another could be Trunks teaming up with a character from a different anime in the Dragon Ball Z world to fight a new, powerful enemy. Maybe a character from Naruto who has unique jutsu skills that could combine with Trunks' power in an interesting way.
One possible plot idea could be that Naruto, in his world, somehow discovers the story of Future Trunks. He might be inspired by Trunks' courage in facing powerful foes alone. Naruto could start training in a new way, emulating Trunks' fighting style. For example, he might focus more on sword - based attacks in addition to his ninjutsu.
One idea could be that Trunks discovers a new power while on a mission, and Bulma helps him control it in a unique way. Maybe she creates a device that can enhance his power but also has some unforeseen side effects that lead to some comical and heartwarming moments between them.