You can also combine different concepts. Maybe Izuku has a quirk that is a mix of telekinesis and heat generation. He could move objects with his mind while also heating them up, creating a powerful offensive and defensive ability. This would require him to train hard to control both aspects of his quirk effectively.
First, consider their motivation for using the Copy Quirk. Are they using it to become the best hero? Or maybe to prove themselves to someone? For example, if they want to be like their idol hero, they might copy only the quirks of that hero at first. Then, think about the limitations of the quirk. Maybe they can only copy a quirk for a short time, so they have to strategize when to use it. This would force them to study different quirks and opponents carefully.
One great Izuku fanfiction is 'A Different Path'. In this story, Izuku gets a quirk that's not One for All but something entirely unique. It shows his journey of self - discovery and how he still manages to be a hero in his own way. The author does an amazing job of exploring Izuku's character and his relationships with other characters like Bakugo and All Might in this new scenario.
The Izuku Luck Quirk in fanfiction could also impact his training at U.A. His luck might make him find rare training materials or encounter mentors who were not part of the original story. This could accelerate his growth as a hero. Moreover, his relationships with classmates could be different. His luck could make him seem more mysterious to his peers. Some might be jealous of his quirk, while others might be curious and want to team up with him more often. This would lead to a different dynamic within Class 1 - A.
First, think about how the voice quirk affects communication. For example, it could be a voice that can hypnotize others or a voice that can shatter objects. Then, consider the OC's personality. A shy OC with a powerful voice quirk could have an interesting internal conflict. Also, think about how this quirk fits into the My Hero Academia world. Maybe the quirk is seen as dangerous and the OC has to hide it at first.
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.
The 'Underdog to Hero' trope is also common. Even when Izuku has a new quirk, he often starts off being underestimated. He has to prove himself not only to his classmates but also to the heroes around him. This trope is great for character development as we see Izuku grow in confidence and skill.
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.
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.
His relationship with Bakugo would likely change significantly. Bakugo might initially be jealous of Izuku's unique shadow quirk. But over time, they could develop a more competitive but respectful relationship, as Izuku's shadow quirk gives him new ways to fight. With his friends like Uraraka, Izuku's new quirk could make him seem a bit more mysterious. Uraraka might be curious about how his quirk works and they could bond over her trying to understand it.
Well, if Izuku had a quirk in a fanfiction, he might be an even more formidable hero. He could have a quirk that combines elements of his original quirkless determination and a newfound power. For example, maybe he has a quirk that allows him to enhance the quirks of those around him while also having his own unique ability, like super strength. This would change the dynamic of his relationships with his classmates. He wouldn't be the underdog in the same way, and might take on a leadership role more quickly.