One idea could be a story where Paladin is hired to protect a young inventor who has created a revolutionary device but is being hunted by a powerful industrialist. Another could be a tale where he teams up with an old acquaintance from his past, a Native American warrior, to stop a group of outlaws who are raiding both white and Native settlements. Maybe a plot where he has to solve a mystery in a small town that seems haunted, but is actually the result of some underhanded scheme by a local landowner.
A plot could revolve around Paladin being wrongly accused of a crime he didn't commit. He has to clear his name while still on the run from the law and the real culprits who are trying to frame him for good. Or perhaps he gets involved in a family feud, where two wealthy families are at each other's throats over an inheritance. Paladin has to figure out a way to end the feud without taking sides. He could also be hired to rescue a kidnapped diplomat from a group of bandits who plan to use the diplomat as a bargaining chip in a political game.
A great plot for a Gun Gale Online OC fanfiction could involve an OC who is a new player but has an incredible natural talent for the game. They quickly rise through the ranks, but this attracts the envy of some of the more established players. So, they have to deal with not only the challenges of the game but also the politics among the players. They might form alliances with other outcasts in the game to overcome these obstacles and show that newbies can be just as good, if not better.
Perhaps in the fanfiction, Hermione uses a gun that was created by a dark wizard but she manages to turn it into a weapon for good. She could be on a mission to stop a group of rogue wizards who are using both magic and muggle weapons to cause chaos. This would involve her learning about muggle technology in a way she never had before and combining it with her magical knowledge.
One plot idea could be that the Gun Mage is a new student at Hogwarts. They have to hide their gun - based magic from the teachers at first because it's so different from traditional magic. Eventually, they use their unique skills to help Harry Potter and his friends in a battle against a new dark force. For example, the Gun Mage's ability to quickly fire concentrated magic blasts could be useful in fending off hordes of dark creatures.
They could team up to take down a powerful and corrupt organization in the Gun x Sword world. Van's strength and Wendy's intelligence would be key assets in this fight.
One idea could be Yoda traveling back in time to train Anakin Skywalker differently, thus preventing his fall to the dark side. Maybe he goes back to the very beginning of the Jedi Order to gain more knowledge about the Force and bring it back to his own time.
One idea could be Shinji traveling back in time to prevent the Second Impact. He might try to change the actions of his father that led to it. Another could be Asuka traveling to a future where the Evangelions have been completely forgotten and she has to figure out how to get back to her own time.
Another plot could be a character from the future coming back to the present in Shameless. They could be trying to stop a future disaster that is somehow linked to the Gallagher family. This would involve a lot of mystery and intrigue as they try to figure out what the future event is and how to prevent it while dealing with the chaos of the present - day Gallagher family.
One idea could be Goten traveling back to the Saiyan - Saiyan war era. He could end up changing some small events that have big impacts on the future, like uniting some Saiyan clans earlier. This would create a whole new timeline where relationships between characters are different.
Maybe a character travels forward in time and sees a dystopian version of the ACOTAR world. They then have to go back and try to prevent the events that led to that future. They could face many challenges along the way, like not being believed or having to work against powerful forces who benefit from the future they saw. It would be a race against time to save their world.
A possible plot for 'Haikyuu time travel fanfiction' is that Tsukishima travels back to his childhood when he first started to dislike volleyball. He could then understand why he developed that negative feeling and change his attitude from the start. This would lead to a much stronger Tsukishima in the present day. Another idea is that a team manager travels back in time to recruit a different set of players for the team, creating a completely different team dynamic. Maybe they could even bring back an old - school player who had unique skills that could revolutionize the team's playing style.