Devil fruits are special fruits that grant their users unique powers. Each devil fruit has a different kind of ability, which makes it difficult for a person to choose a single fruit. In One Piece many characters have openly stated that a person can only eat one devil fruit.
So, if a person ends up eating a devil fruit that they don't like, they will have to live with it for the rest of their life. There is an exception to this rule as Blackbeard has two devil fruits, which makes him a special case. With One Piece heading towards its final saga, there are still plenty of devil fruits that the fans are yet to see.
6 Water-Water Fruit
The biggest weakness for devil fruit users is water, and considering that most of them are pirates, it is a big issue for them as the seawater can instantly weaken them and render them useless.
If someone gets the Water-Water Fruit, they can easily manipulate all kinds of water sources and since most pirates fight on the seas, it would give the user of this devil fruit a significant advantage. This devil fruit has not been introduced in the series yet, and the chances of it being revealed further down the line are slim.
5 Wind-Wind Fruit
The Wind-Wind Fruit has been one of the most speculated devil fruits within the One Piece community. The mention of this devil fruit goes years back when certain fans started to believe that this devil fruit might actually belong to the infamous Monkey D. Dragon.
Most of the theories speculate that the devil fruit was eaten by Dragon as whenever he appeared in the series, the weather has been disrupted. Of course, if this is the case then it won't be long until Dragon finally shows off this power as the series is getting close to its end.
4 Mythical Zoan Cerberus
In the Wano Country arc, a lot of zoan-type devil fruits were revealed. The fans were expecting Kaido's crew to have more than just one mythical zoan-type devil fruit, but it never happened. The series only has a handful of mythical zoan-type devil fruits, so it would be great if Oda introduced more of the same kind.
The Cerberus is a mythical beast from Greek mythology. It has a dog's body, but instead of just a single head, it has three. A lot of theories speculate that this devil fruit might actually belong to Blackbeard with the reason being that just like the three heads of the Cerberus, Blackbeard has three skulls on his jollyroger. Also, this could explain why Blackbeard is able to wield two devil fruits at the same time if it was the first devil fruit that he consumed.
3 Teleportation
The power to instantly reach a certain place cannot be overlooked. Any kind of devil fruit that would grant such power would undoubtedly be very strong. If such a devil fruit were to exist then it would undoubtedly be a paramecia-type devil fruit.
This devil fruit has been rumored to be in the possession of Shanks, who is one of the Yonko. On various occasions, Shanks has appeared mysteriously at different locations. During the Marineford arc, Shanks managed to intercept Kaido and his crew and prevented them from coming to Marineford. Then he somehow managed to appear at Marineford and stopped the war. Later in the series, Shanks was seen in Mary Geoise, which is off-limits to almost every person.
2 Mythical Zoan Gryphon
Griffin or Gryphon is an extremely popular mythical character, and it has appeared in various mythologies, which include the Greeks, Romans, and many central Asian cultures. The griffin has largely been associated with guarding treasures. Over the years, the griffin became a symbol of divine power. The griffin is usually drawn with the head and wings of an eagle and the legs, tail, and body of a lion.
Shanks' sword is named Gryphon, which is what the griffin is sometimes called. While Shanks is considered to have no devil fruit, it is possible that his sword could have eaten this devil fruit. This is not impossible as we have seen inanimate objects having the power of devil fruits. If Oda does go down this route, it would maintain the fans' headcanon that Shanks does not have a devil fruit.
1 Plant-Based Logia
One Piece mainly has devil fruits that are based on animals. Throughout the entire Wano Country arc, the fans saw plenty of zoan-type devil fruits. These devil fruits were not just limited to the currently available animal life, but they also included several ancient creatures such as dinosaurs and even mythical beasts such as dragon, phoenix, and even a literal God.
There is no doubt that all the zoan-type devil fruits are amazing, but there is no doubt if Oda actually added a plant-based devil fruit, it would be extremely unique. The devil fruit could be a logia type that could allow its user to sprout different parts of a plant. It could be similar to Wood Release from Naruto. After the recent chapter, there is a strong possibility that Admiral Ryokugyu might actually have this devil fruit.