One cool quirk idea could be 'Shadow Mimicry'. The user can blend into any shadow and move freely within the shadow realm, also being able to mimic the actions of those whose shadows they are in. It gives a lot of stealth and surprise attack possibilities in a fanfiction.
One idea could be a fanfiction where Deku's quirk suddenly mutates. Instead of just having One For All, he starts to develop an additional power related to it, like the ability to share a fraction of One For All's power with his friends temporarily to boost their own quirks in a time of great need.
The 'Plant Symbiosis' quirk would be a great addition to a fanfiction. The individual with this quirk can form a symbiotic relationship with plants. They can communicate with plants, make them grow rapidly, and even use plants as an extension of their body for things like creating shields or lashing out at enemies. This quirk could bring a whole new element of nature to the story.
One idea could be fusing Bakugo's explosion quirk with Todoroki's ice quirk. Imagine a hero who can create explosive ice shards. It would be a visually stunning and powerful ability. Another could be fusing Uraraka's zero - gravity quirk with Midoriya's One For All. The hero might be able to make objects weightless and then send them flying with super strength.
One idea could be to make the character with the lightning quirk have a fear of water. This would add an interesting dynamic as lightning and water don't mix well. They could struggle to control their quirk when near water, and it could be a source of internal conflict for them.
One idea could be that Izuku's quirk is related to time manipulation. He could use it to slow down time during battles, giving him an edge in combat. For example, he could dodge attacks with ease and plan his counter - attacks carefully.
His quirk could be something like 'Limitless Rage - Transformation'. When he gets angry, his body transforms into the Hulk form, growing in size and strength. The angrier he gets, the more powerful he becomes, similar to how it works in the Hulk's original story.
One idea could be a villain who can steal quirks and is secretly a former hero trainee who was wronged. They start stealing quirks to create a super - powerful army to take revenge on the hero society that failed them.
Perhaps a story where a Copy Quirk hero is framed for using villainous quirks they copied in self - defense. They then have to go on the run and prove their innocence. Along the way, they meet other outcasts and form an unlikely team. They use their copied quirks in creative ways to avoid capture and expose the real villain who set them up.
One idea for a Deku's Quirk fanfiction could be exploring what would happen if Deku's quirk manifested in a different way. For example, instead of having to gradually control One For All, he suddenly has full mastery from the start. This could lead to a very different story arc where he is immediately seen as a top - tier hero - in - training, causing envy and admiration in equal measure among his classmates.