Luffy's rubber powers are a result of eating the Gum-Gum Fruit,[20] which makes him virtually immune to nearly every blunt force and electric-based attack, and grants him the ability to stretch his body at will. Combined with the elasticity of his body, he uses that ability to accelerate parts or the whole of his body as if shot by a slingshot to deliver punches, kicks, head butts, body checks, or simply for propulsion. As with other Devil Fruit users, Luffy is unable to swim and when he is submerged in water it can negate his powers, as well as Sea Prism. In addition to his Devil Fruit powers, Luffy possesses immense strength and endurance.
Luffy's signature move is the Gum-Gum Pistol (ゴムゴムの銃ピストル Gomu Gomu no Pisutoru?), a punch technique which he learned during his years of training. Another technique developed later in the series, is Second Gear (ギア2セカンド Gia Sekando?), a technique that increases his strength and overall speed for a limited amount of time, but can strain his body afterwards. By observing the Shave (剃 Soru) technique of CP9, Luffy was able to adapt the move with his own rubber body, matching the speeds of the elite assassins. Third Gear (ギア3サード Gia Sādo), another technique, uses air inflated into his bone structure to attack with massive limbs and strength, but initially causes him to shrink afterwards.[21] He is capable of using both techniques simultaneously. After two years, Luffy has gained better control over these techniques and is no longer affected by their drawbacks. Eventually, Luffy develops his latent ability to use Haki (覇気, lit. "ambition"). This ability has two main types: Armament Haki (武装色の覇気 Busōshoku no Haki), which is an armor-like force that can amplify defense and the force of attacks and negate a Devil Fruit user's defense, allow physical contact and damage, and Observation Haki (見聞色の覇気 Kenbunshoku no Haki), which is a sixth sense that can read a person's moves and detect their presence. He also has a rare third type, the Conquering King's Haki (覇王色の覇気 Haōshoku no Haki) which can render people or animals in his proximity unconscious. [22] Two years later, Luffy masters the three types of Haki, and uses them in conjunction with his improved attacks. Also, as a result of his encounter with Magellan, Luffy has also developed an immunity to poison. He also develops another technique, Fourth Gear (ギア4フォース Gia Fōsu) which is similar to Gear Third as Luffy inflates his muscles to increase the size of his limbs (except his legs) and imbues his arms and chest with Armament Haki, engulfing other parts of his body with it as well when needed. In this state, Luffy can execute highly destructive moves by compressing his limbs then releasing them instead of stretching. He can also fly in this state in a similar fashion to CP9's Moon Walk (月歩 Geppō) technique.[23]