Nui Nui no Mi

The Nui Nui no Mi is the conjectural name for a Paramecia-type Devil Fruit that grants the user the ability to stitch things together and un-stitch them like nothing happened. "Nui" (縫) means "to sew" or "to stitch". It was eaten by Leo.

Strengths and Weaknesses
This fruit allows the user to stitch things to something like the ground. It is very useful in pinning people to the ground such as how Leo was able to restrain Robin to the ground. The user is also able to undo the stitches to the object, as seen as when Leo undid the stitches on Robin. However, the stitches do not harm its victim and do not appear to physically puncture the object. The stitches are strong enough to hold Robin down.

This fruit does not have any known specific weakness besides the general Devil Fruit weaknesses. However, a sewing needle is needed for the ability to actually work.

Usage
Leo basically uses this power to stitch and hold down his targets. He also uses this ability to support objects, during earthquakes, to make sure they do not fall.

Trivia

 * As with the Mato Mato no Mi (which was referred to as the "Mato Mato Curse"), this fruit has not yet actually been named in the manga. Unlike the Mato Mato no Mi, it has not been expressly confirmed to be a Devil Fruit. Leo referred to his "magic" as the "Nui Nui" power ("ぬいぬい"の力), notably in hiragana rather than the katakana used in all Devil Fruit names. Despite this, the name has the same repeated two syllable word structure as all other Devil Fruits, and the nature of the ability clearly points towards it being a Paramecia fruit.
 * The user seems to require an external object, in this case, the needle to use his powers. However, the string he uses to stitch things seems to be from his own creation, as no source of strings were seen whenever he used his powers. It is also unknown if the user can stitch himself.