Perhaps the OC with plant powers has to defend a magical garden from dark forces. The plants could transform into warriors or create barriers to keep the intruders out. It could be a story full of action and magic.
Often, there might be a villain. This could be someone who wants to use the power of the plants for evil, like a dark sorcerer who wants to drain the life from the plants to gain more power for themselves. And of course, there would be friends of the OC, maybe other people with different powers who team up with the OC to protect the plant - powered world.
Another plot might involve Dipper having to keep his powers a secret from his family and friends at first. He struggles with this as he tries to figure out how to control them without raising suspicion. For example, he accidentally makes things levitate when he's around Mabel, and has to quickly cover it up.
Maybe Naruto's god powers allow him to travel through different dimensions at will. He could visit the Otsutsuki home planet and learn about the true origin of chakra, and then bring that knowledge back to Konoha to revolutionize ninja training. He might also encounter other god - like beings in these dimensions and have to prove himself.
Another plot could involve the OC king's relationships. He might have an unexpected alliance with a powerful but previously hostile house through a marriage of convenience. This could lead to a whole new power dynamic in Westeros as they combine their forces. Or perhaps he has a secret friendship with a commoner who becomes his most trusted advisor, which goes against the traditional norms of the land.
Maybe there's a plot where the OC and Matt team up to expose a medical malpractice in the hospital. They face a lot of obstacles together, which makes their relationship more complex and interesting.
One interesting plot could be the challenges the OC faces while being pregnant in a world full of supernatural elements like Damon's. Maybe she has to deal with vampire enemies who see her unborn child as a threat. Another could be Damon's struggle to protect the OC and the baby, as his vampire nature might put them in danger at times.
There could be a plot where the OC is from another dimension. This OC has special powers and lands in Gotham. Batman initially suspects the OC but as time passes, they start to trust each other. Meanwhile, characters like Poison Ivy and Harley Quinn are drawn to the OC's otherworldly charm, leading to the formation of a harem. The group then has to deal with threats that cross dimensions.
In some 'oc son of goku fanfiction', a common plot is the OC's struggle with his identity. He is the son of Goku, a great hero, but he wants to make a name for himself. So he might embark on a quest to find a new form or a new fighting style that is all his own. Also, there could be a plot where he has to deal with the jealousy of other Saiyans who feel he gets special treatment due to his father.
In some 'pokemon ash and oc fanfiction', the plot might revolve around the OC coming from a different region with a whole new set of Pokemon. This could introduce Ash to new training techniques and Pokemon species that he hasn't encountered before, adding a fresh dimension to his journey.
In some fanfiction, an OC might be a talented artist. She meets Anthony at an art exhibition. The plot could revolve around how Anthony, who is initially only interested in finding a proper wife, discovers a new side of himself through his interactions with the OC. As they spend more time together, he begins to value art and creativity more, and of course, they develop deep feelings for each other.