According to Dr. Vegapunk, Devil Fruits come into existence through imagination or a want for something. Throughout history, there have been countless people who have wished for certain powers to exist. For instance, there have been people who have wished for the power to control fire or the power to control ice.
In Chapter 1044, the Five Elders revealed that Luffy's Devil Fruit was actually the Human-Human fruit, and it's not a Paramecia type. It's a mythical Zoan fruit that allows the holder to transform into, and gain the attributes of, the legendary Sun God Nika.
These artificial Devil Fruits, known as SMILEs, were developed by Caesar Clown and Donquixote Doflamingo.
The Hana Hana no Mi is a powerful Paramecia-type of Devil Fruit eaten by Zoro's crewmate, Nico Robin. This Devil Fruit allows the user to sprout any part of their body from anywhere. With advanced control, the user can even create an entire clone of themselves.
One of the many snake Fruits seen in One Piece, the Yamata no Orochi version is considered to be the rarest out of them all. It was eaten by the Shogun of Wano, Kurozumi Orochi, and it grants him the ability to transform into an eight-headed serpent, each head having its own personality.
The Mizu Mizu no Mi (lit Water Water Fruit) is a Logia-type Devil Fruit that allows the user to control and become liquid water.
The first time we saw a devil fruit was in the fourth anime episode (the first manga chapter) of One Piece. It was Luffy's Gomu Gomu no Mi devil fruit.
A SMILE fruit is intended to grant the consumer the power of animal transformation, much like a Zoan-type Devil Fruit, by a process which involves transmission of the Lineage Factor of a real animal. Like normal Devil Fruits, SMILEs render those who consume them unable to swim.
One Piece shows a new awakening of a Zoan-type Devil Fruit, confirming that Luffy's version of this rare and powerful ability is absolutely unique.
And then later on he ate the two fruits and cuz of his sleeping disorder the two devils wouldn't fight each other.
The Gura Gura no Mi is considered the strongest Paramecia devil fruit of all for its absolute destructive powers. Whitebeard earned the title of the “Strongest man in the world” with this devil fruit.
Artificial Devil Fruits are man-made fruits designed to give consumers special powers like a natural Devil Fruit would. The creation of artificial Devil Fruits has been attempted by two scientists, who once belonged to the research institute MADS: Vegapunk and Caesar Clown.
Shanks is the only member confirmed to have not eaten a Devil Fruit. Shanks is the only member who is not an Admiral of a Fleet. Shanks is the only member of the original Four Emperors to not be a member of the Rocks Pirates.
All Devil Fruit eaters lose their ability to swim after consuming the Devil Fruit. It's not just a loss of muscle memory; entering a body of water saps them of all energy. Even entering a bath can drain a Devil Fruit eater of energy and prevent them from using their abilities.
The Sugi Sugi no Mi, coming from "suigin," Japanese for mercury, is a Logia type Devil Fruit which allows the user to dissolve entirely into a pool of quicksilver. This fruit was eaten by Marine Admiral Calomel.
"A person who has devil fruit power experiences a lack of energy when gets into the water!" That means, the user lacks minimum energy to show body movements, otherwise, they could swim. Without body movement, the person starts sinking down.
To everyone's surprise, Luffy, who was always believed to be a user of the Paramecia type Gomu Gomu no Mi, is actually a user of a Zoan type Devil Fruit. Furthermore, this isn't just any Devil Fruit, but a power described to be "the most ridiculous" to exist in the entire story.
The Nami Nami no Mi is a Paramecia-type Devil Fruit that allows its user to become a "Tearful Woman" (涙の女, Namida no On'na) as it enables them to change the the properties of their tears.
Trivia. Sanji claimed that he wanted to eat the Suke Suke no Mi because he wanted to be a superhero (though in reality, he just wanted to peek at women while they are bathing). Sanji hated Absalom even more because he ate the Suke Suke no Mi.
With the Pika Pika no Mi, Sanji's Powers would grow even further and make him the fastest man alive. Furthermore, this would also make his kicks more dangerous than ever before. Sanji would be able to kick at the speed of light and that would mean his kicks become deadly.