Gomu Gomu no Mi

The Gomu Gomu no Mi is a Paramecia-type Devil Fruit that gives the user's body the properties of rubber, making the user a Rubber Human. It was originally a treasure that Shanks and his crew took from an unspecified enemy, but was accidentally eaten by the series protagonist Monkey D. Luffy. In the second version of Romance Dawn, it originally belonged to Luffy's grandpa who took it from an unspecified enemy

The fruit's major strength, as demonstrated by Luffy, is that the person's body can stretch like rubber even when the ability user himself is nullified (for instance, when Nojiko pulls Luffy's head out of the water at Arlong Park). It also makes them almost entirely immune to blunt attacks, including hand-to-hand combat, bullets or even cannonballs, an ability which can be further reinforced with the application of Busoshoku Haki. Thanks to Luffy's own creativity both in and out of combat, this fruit has consistently proven itself to be among the most formidable, versatile, and unpredictable within the Paramecia class. The user's rubber-like body also allows the user to survive falls from heights and collisions that would kill a normal person.

Luffy's rubber body not only allows him to hit Enel, whose body is made of electricity, but also prevents Luffy from suffering electric shocks.
The user's ability to stretch and twist like rubber to extreme lengths not only makes him immune to injuries that originate from such, but it also allows him to even rebound, that can give him a great advantage in or out of battle. Stretching also allows the user to drastically increase the range of what would otherwise be considered a powerful close-range attack, turning it into a devastating mid-range or long-range attack. A stretched limb can also be used to store potential energy like a stretched spring, increasing the velocity by stretching his arm back resulting in increased power. Combined with Haki, his power is increased even more. Owing to rubber-like natural insulating properties, the user is also immune to electrical attacks and is also able to hit an electric Logia user without Haki.[9] Additionally the user is immune to the electricity produced by Electro.

Luffy's body is similar to a rubber band, requiring him to use excessive motion to "throw" an attack. After the time-skip though, the extra movement is unnecessary, and Luffy is able to stretch easily.

In the first SBS, Oda stated that Luffy's maximum stretching distance is 72 Gomu Gomus.[10]

By training his abilities, Luffy has found unexpected ways to increase his fighting ability, such as the ability to stretch his blood vessels wider to increase the speed of his blood flow in order to become faster and stronger, at a cost of depleting his body's energy at a faster rate. Furthermore, with the application of Haki, he is even capable of igniting a limb for an even more devastating attack. Luffy can even inflate his bones to increase the volume of his body and significantly increase his attacks, at the cost of his body becoming smaller for a short period of time (although after the timeskip Luffy has seemingly been able to overcome this weakness as after he used "Gomu Gomu no Elephant Gun" on the Kraken and he did not revert to his smaller size afterwards).

The fruit enables all parts of the consumer's body to behave like rubber, including organs. As such, Luffy has a bigger appetite than the average human, eating more than anyone else in his crew and always digesting it before anyone else is hungry again.

Despite all the great advantages Luffy gets by using his fruit, he can however still be hurt by cutting or stabbing attacks, as well as non-physical attacks such as fire or ice. One major risk of Luffy's powers is that he is vulnerable to attacks in the moments when his limbs are stretched to their limit, as Buggy and Kuro both demonstrated early on in the series. Luffy, however, has adapted his fighting style to minimize this risk as shown when Buggy attempted to exploit this weakness of Luffy.

Luffy has also shown a limited ability of moving in mid-air, by grabbing onto something with an extended limb and propelling away from what could have been a fatal attack. This gives Luffy the option of several jumping and mid-air attacks that would have been disadvantageous to most other people as it would have left them vulnerable.

In his youth, Luffy had a problem controlling his own abilities. Though he had an idea of how they would work, Luffy had trouble with aiming and the timing of his attacks, and he was continuously sent spinning by the recoil. However, he managed to counter these weaknesses with his continuous training in the jungle by the time he left to be a pirate.

In the anime, Luffy has used his stretching abilities to inhale great amounts of air to thus exhale a big gust of wind; this application of his powers was used to blow away Marigold's poisonous vapor from her venom spit and Magellan's poison breath.

Given Luffy's elastic properties he is shown to be able to withstand great pressure, as shown near Fishman Island when fighting Hody. Though he was still weakened by the sea water around him, he was seemingly unaffected by the intense underwater pressure.