The Ope Ope no Mi is, without a doubt, one of the strongest and most coveted Devil Fruits in the entire One Piece universe. This Paramecia-type fruit is frowned upon for its special abilities that tend to blur the thin line separating medical science from supernatural power. The fruit per se has a very unique appearance in the form of a small, red, heart-shaped fruit resembling a strawberry. It has a stem with a swirl at the end, easily recognizable among the many Devil Fruits in the series.
Ope Ope no Mi has several astounding abilities all circled around the concept of an "operating room." The primary power of this fruit involves the ability to create a spherical space, known as a "Room," in which the user can gain incredibly fine control over everything inside. This Room is the base for most of the fruit's other abilities, which let one move objects, but even living beings within its boundaries.
The abilities that the user of the Ope Ope no Mi can execute inside the Room are those so extraordinary to the point of defying some of the natural principles of physics and biology, notably being able to disassemble and reassemble objects and bodies at their whim. This basically allows them to conduct instant surgery or editing on any body.
This power is powerful to such a degree that a user is able to remove hearts from bodies without killing a person and slice individuals into segments but stay alive, and further exchange personalities across different bodies. This manipulation one is allowed to do in the Room is often described as being able to do 'nearly everything a doctor might do,' but at a pace and scale way beyond what any normal medicine would allow.
One of the most interesting powers of Ope Ope no Mi could be its eternal youth potential. Such powers are often called the "Perennial Youth Operation," and it is said to be the ultimate technique of the fruit. Of course, there will have to be a cost to it: a life in exchange for eternal youth. This sacrifice reveals the unbelievable power of this fruit and the type of moral dilemmas it can unleash, so it is something very interesting and controversial within the One Piece world.
While the Ope Ope no Mi does not only have simple uses in medicine, its users are capable of moving the space inside one's Room as one wills, thus teleporting objects or people from one place to another. This also includes making barriers for defense against enemies or flying. This mix of medical abilities with spatial movement makes this fruit so valuable in combat and regular life.
The Ope Ope no Mi is considered the "Ultimate Devil Fruit" due to its extraordinary abilities. It is so powerful that it drove the plot of several arcs in One Piece as various factions want to get or control it. Most especially desirable to those in power, this fruit offers the possibility of immortality, hence adding a layer of political intrigue in this existence of the series.
The Ope Ope no Mi user currently known in the One Piece series is Trafalgar D. Water Law, who has been quite a character in spreading the potential held within the fruit right from the story. Having mastered the powers of this fruit, Law turns into one of the most powerful and unpredictable characters in the whole series, capable of turning the tides in every battle and the flow of events with his special abilities.
Within the world of One Piece, the Ope Ope no Mi comes up with numerous questions over life, death, and the main sense in the exercise of power. The power of the fruit to oversee life itself and grant immortality places it central to the philosophical debates running in the series. The fruit symbolizes the ultimate medical achievement, classifying it as a warning of the hazards of 'playing god' in people's lives.