Mera Mera no Mi

The Mera Mera no Mi, also known as the Mera Mera Fruit, is a Logia type Devil Fruit that allows to user to transform into fire at will as well as control it. "Meramera" is the noise a fire makes when it burns. In the 4kids adaption, it is called the Flare Flare Fruit. However, in the Viz Manga, it is called the Flame Flame Fruit. It was eaten by Portgas D. Ace. Its powers were first hinted at when Ace visited a town in Drum and apparently caused the snow to temporarily stop from falling there for a day.

Strengths and Weaknesses
The fruit's major strengths like other Logia types allows the user to produce as well become the element they control. In this case, Ace is able to create, control, and become fire. With this in mind, Ace is able to create fire-based attacks. He is also able to avoid normal attacks by turning into fire and allowing the attack to pass through him. Turning into fire also has the added effect of burning an opponent depending should the attack be closed range and such.

While there hasn't yet been any other unique weaknesses revealed that may affect the fruit solely outside speculation, the fruit's powers however were the first to be revealed to be weak against the Yami Yami no Mi during Ace and Blackbeard's battle. When touched by Blackbeard, the powers of the fruit were negated and Ace was unable to turn into fire. This allowed Blackbeard to inflict an attack on Ace that would've normally been avoidable. However, despite this circumstance, the fruit's powers are still able to inflict damage onto Blackbeard. The full extent of damage inflicted by Ace's ultimate move, if any, onto Blackbeard have yet to be revealed, although it's known that Blackbeard at least survived.

Usage
The fruit's bestowed powers, as used by Ace, have been used for a variety of ways. Ace notably uses them usually either to fight or to propel his raft. During Ace's cover story, the powers of the fruit allowed Ace to rescue a Marine officer and some documents on board a burning ship. Despite being weakened by the Yami Yami no Mi severely during his fight against Blackbeard, Ace was still able to skillfully use the fruit's power to inflict some damage to his former subordinate. The named techniques that are used by Ace that involve the Devil Fruit are as follows:
 * Kagerou (Heat Haze): Ace shoots a stream of fire from the palm of his hand. This was first seen being used to stop Smoker from catching Luffy.


 * Hiken (Fire Fist): Ace turns his fist into flames and launches it as a column of fire at his target. This attack is incredibly powerful that it is able to plow through several ships in one shot. It is apparently the source of Ace's alias of "Fire Fist Ace." This is called Heat Fist in the 4kids dub and Flame Fist in Funimation dub.


 * Higan (Fire Gun): Pointing the index and middle fingers of both hands at an opponent like guns, Ace turns his fingertips into flames and shoots bullets made of fire at them. This technique was first seen when Ace retaliated against Van Auger's attack.


 * Enkai (Flame Commandment): Ace amasses a large amount of flames around his body in preparation for an attack. This is apparently the prerequisite technique before Ace can use Hibashira.


 * Hibashira (Fire Pillar): Used following Enkai. Ace shoots the collected flames straight upward, destroying a target above him. This technique and its prerequisite technique were first seen when Jesus Burgess threw a hotel at Ace.


 * Hotarubi: Hidaruma (Firefly Fire: Body Covered in Flames): Ace creates many small fireballs that float around an enemy before flying into them all at once, burning them. The idea behind this attack's name is that before he attacks with them, the small fireballs look like fireflies in the air. This was first seen being used in Ace's battle against Blackbeard after Blackbeard performed his initial attacks.


 * Shinka: Shiranui (Sacred Fire: Mysterious Light at Sea): Ace launches two long lances made of fire at his opponent's chest. The lances have the combined effect of simultaneously burning an opponent while piercing their chest. This was first seen being used against Blackbeard when Ace was being dragged by Blackbeard's power.


 * Juujika (Cross-fire): Ace puts his index fingers together in a cross shape before launching a cross-shaped column of flame directly at his opponent. This was first seen being used against Blackbeard after Ace attacked Blackbeard with Shinka: Shiranui. This attack's name is a pun since "Juujika" refers to crossfire from weapons, yet Ace is making an actual cross out of fire.


 * Daienkai: Entei (Great Flame Commandment: Flame Emperor): Ace's ultimate technique. Ace creates a gigantic fireball resembling the sun and hurls it at his opponent to try to obliterate them. This was first seen being used during the final moments of Ace and Blackbeard's battle, note that "Entei" is a homynim with "Enkei" meaning "circle", a reference to the attack's shape.