The purpose of ninjutsu is to enable ninja to perform their duties efficiently, primarily intelligence gathering and taking down enemies. Ninjutsu particularly aids ninja with stealth operations, as several techniques focus on making discreet escapes and swiftly incapacitating enemies a practitioner may encounter.
Many ninja use weapons, with shuriken being the most common. Others have been seen using swords and ropes.
Ultimately, a very large variety of techniques have been dubbed as "ninjutsu", with the only real aspect tying them together being their usage by professional ninja. When Jigoku Benten fired a gun and dubbed the attack as a ninpo technique, Zoro questioned whether it actually was one. Due to Wano's lack of knowledge about Devil Fruits, those powers and their specific applications and techniques are usually referred to as "jutsu" by their users. Additionally, there have occasionally been gags where ninja refer to simple actions as ninjutsu techniques or claim to be performing mystical arts to create an effect that was actually caused by something else.
Ninpo: Enton no Jutsu (忍法 煙遁の術,Ninpō: Enton no Jutsu?, literally meaning "Ninja Art: Smoke Escape Technique"): User throws a smoke ball into the ground and quickly moves to a new location while being obscured by the smokescreen. The technique was first used on Zou as part of a demonstration of Raizo's ninja abilities. Later, it was used by Shinobu against Yamato which allowed her to escape, not believing the latter claim to want to help her protect Kozuki Momonosuke. While used by Shinobu, she dropped the part of "Ninpo".
Ninpo: Kanashibari no Jutsu (忍法 金縛りの術,Ninpō: Kanashibari no Jutsu?, literally meaning "Ninja Art: Paralysis Technique"): A technique which allows user to paralyze their enemies. It was first "used" against Hanzo as a gag technique by Shinobu, although he had already been incapacitated by the pain from her Ball-Crusher technique, leading Nami to question whether it was an actual technique. Later during the fight between Raizo and Fukurokuju, it is not a gag technique but actual technique which is effective. Both of them used this technique to paralyze each other by circling their index fingers and thumbs.
Ninpo: Bunshin no Jutsu (忍法 分身の術,Ninpō: Bunshin no Jutsu?, literally meaning "Ninja Art: Clone Technique"): A technique utilizing the power of the Maki Maki no Mi. Raizo unrolls multiple scrolls on the ground below him, and drawings of himself manifest from the scrolls, becoming lifelike clones which move around him and thus confuse opponents as to where the real Raizo is. The technique was first used on Zou as part of a demonstration of Raizo's ninja abilities, though it was not shown to be a scroll-based technique at the time. The usage of the scrolls was first seen when Raizo used this technique during his battle with Fukurokuju.
Ninpo: Daisuki no Jutsu (忍法 大好きの術,Ninpō: Daisuki no Jutsu?, literally meaning "Ninja Art: Loveable Technique"): Raizo leaps into the air and offers a hug.
Ninpo: Maki Maki no Jutsu (忍法 巻々の術,Ninpō: Maki Maki no Jutsu?, literally meaning "Ninja Art: Scroll-Scroll Technique"): Raizo uses the power of Maki Maki no Mi to manifest a scroll from thin air that can capture and store an enemy's attack inside of it. The scroll starts out normal-sized but can rapidly grow in size to intercept any attack. It was first used to intercept Kaidou's Bolo Breath attack.
Hokan (奉還,Hōkan?, literally meaning "Restoration"): After wrapping the scroll around his opponent, Raizo releases their attack from the scroll to strike them across their whole body. Before unleashing this attack, Raizo says "Return" (お返しいたす,Okaeshi itasu?) followed by the name of the opponent's attack. It was first used against Kaidou to redirect his Bolo Breath attack back at him.
Ninpo: Kawarimi no Jutsu (忍法 変わり身の術,Ninpō: Kawarimi no Jutsu?, literally meaning "Ninja Art: Body Replacement Technique"): Raizo replaces his body with a large log and reappears somewhere else, allowing him to escape an attack.
Ninpo: Musasabi no Jutsu (忍法 ムササビの術,Ninpō: Musasabi no Jutsu?, literally meaning "Ninja Art: Flying Squirrel Technique"): Raizo glides through the air with his arms stretched out. He uses this to escape from Solitaire.
Ninpo: Odako (忍法 大凧,Ninpō: Ōdako?, literally meaning "Ninja Art: Big Kite"): Shinobu uses a large kite to evade pursuers through the air. It is large and durable enough to carry at least one additional person with Shinobu. It was first used to escape a home of an individual on whom Shinobu and Nami were spying.
Ninpo: Kintama-Tsubushi (忍法 金玉潰し,Ninpō: Kintama-Tsubushi?, literally meaning "Ninja Art: Ball-Crusher"): Shinobu throws an object that ricochets to hit her opponent's groin. It was first used against Hanzo of the Orochi Oniwabanshu.
Sexy Ninpo: Kare-San-Sui (熟々忍法 枯散衰,Sekushī Ninpō: Kare San Sui?, literally meaning "Mature-Mature Ninja Art: Wither-Scatter-Decline): Shinobu touches the ceiling in which she hides and makes it collapse with the Juku Juku no Mi in order to escape. In the VIZ translation, this is called Sexy Ninpo: Rot Garden. The technique's name may be a pun on karesansui (枯山水,karesansui?), "dry landscape", a term for the Japanese rock garden.
Jigoku Benten's Techniques
Ninpo: Jigoku Biwa (忍法 地獄琵琶,Ninpō: Jigoku Biwa?, literally meaning "Ninja Art: Hell's Lute"): Jigoku Benten plays her biwa, which contains a hidden gun that fires a quick barrage of shots at her target. It was first used against Roronoa Zoro.
Ninpo: Mimitabu Cracker (忍法 耳たぶクラッカー,Ninpō: Mimitabu Kurakkā?, literally meaning "Earlobe Cracker"): Fukurokuju's signature method of fighting, He controls his earlobes as though they were his arms and uses them to strike opponents with tremendous force like whips, with the earlobes having a considerable amount of range due to their length. In the VIZ translation, this is called Ninpo: Earlobe Crackers.
Nami's usage of her Art of Weather in front of Kin'emon and Raizo on two separate occasions was referred to as "Ninjutsu". Later, while she accompanied Shinobu, she named one of her techniques "Ninpo". Additionally like Shinobu, O-Nami was given the nickname Kunoichi (the name for a female practitioner of Ninjutsu) for her bounty issued by the Mimawarigumi of Wano Country.
When Robin used one of her Hana Hana no Mi abilities before Kin'emon, he associated it with "Ninjutsu". Recently, so did the Orochi Oniwabanshu when they tried to attack 'her' and it was revealed to actually be one of her clones (but they also thought it might be "Sorcery").