An OC human ranger who has the ability to sense the presence of the One Ring from a distance. He is initially distrusted by the Fellowship but proves his worth as he uses his unique skill to help them avoid many perils on their journey with the Ring.
Perhaps an OC dwarf who was exiled from his mountain home due to his obsession with a small piece of mithril that has a strange connection to the One Ring. He then has to navigate the power struggles between different factions while dealing with his own inner demons related to the Ring's allure.
One idea could be an OC who is a descendant of an ancient elven line with a natural resistance to the One Ring's corruption. They could be on a quest to understand their heritage and end up being drawn into the events surrounding the Ring.
Another interesting concept is an OC from a race we haven't seen much in the main story, like the Haradrim, who comes into possession of a ring. They might have a different cultural perspective on the power of the ring and how to use or resist it. This could lead to a story full of political intrigue and cultural clashes within Middle - earth.
Your OC could be a ranger who has a vendetta against a powerful orc chieftain. The orc has been raiding villages and killing innocents. The OC sets out on a mission to hunt down the orc. Along the way, they get involved in a larger conflict between the forces of good and evil. They meet other characters from the Lord of the Rings world, like Aragorn or Legolas. This plot allows for a lot of action and character development as the OC battles their personal enemy while also contributing to the greater fight against Sauron.
One idea could be creating an original character who is a lost heir to one of the kingdoms in Middle - earth. This character could have been hidden away during a great war and now emerges to reclaim their rightful place. Another idea is an OC who is a skilled ranger from a previously unheard - of tribe in the forests. They could cross paths with the Fellowship and offer their unique skills to the cause.
One idea could be that the OC is a healer who joins Aragorn's journey. They meet during a battle where Aragorn is injured and the OC uses their unique healing skills to save him. This starts a bond between them as they travel together, with the OC providing medical aid to the whole fellowship.
Well, you could have an OC whose father was a Grimm researcher. The OC might inherit his father's notes and research, leading them on a journey to understand the Grimm better, perhaps even finding a way to peacefully co - exist with them. Or an OC with a father who was a Dust miner. The father could have been involved in some sort of accident related to Dust, and the OC's story could be about getting revenge or preventing similar accidents in the future. A third idea is an OC whose father was a well - known merchant. The OC could use their father's business connections to gain access to rare items and information for their own adventures.
There's also 'A Ranger's Tale'. This fanfic focuses on an original ranger character. The author does an amazing job of portraying the life of a ranger in Middle - earth. The OC has their own set of skills, beliefs, and a backstory that ties in well with the overall theme of the 'Lord of the Rings'. It has some great action scenes and moments of self - discovery for the character.
Well, perhaps the prophet oc is from a different realm and is brought to Middle - earth. In the fanfiction, they could have a special connection with the One Ring. Instead of being corrupted by it, they use their prophetic powers to understand its true nature and find a way to destroy it without having to go through the long and arduous journey that Frodo had to endure. They could be like a guiding force for the Fellowship, using their knowledge of future events to keep them safe.
A crossover with the Star Wars universe would also be cool. The Jedi could be like the wizards in Middle - earth. Maybe Aragorn could learn some lightsaber skills from the Jedi and use them against the orcs. And the Force could have an interesting interaction with the magic in Middle - earth.
Another way is for the OC to be a rival to the main characters. An OC dark knight who is also after the One Ring, not for the same reasons as Sauron, but for his own power - hungry desires. This creates an additional layer of conflict and danger for the Fellowship as they try to protect the Ring from both Sauron and this new threat.
One idea could be creating an OC who is a master of a unique form of Haki that no one has seen before. For example, a Haki that can manipulate the very air around them to create barriers or attacks. Another idea is an OC that is a descendant of a forgotten pirate crew from the Void Century, and they are on a quest to uncover the secrets of their ancestors. Also, an OC gamer who is actually a reincarnation of a powerful ancient being in the One Piece world, and they slowly discover their past powers and abilities as they adventure through the Grand Line.