Nemu Nemu no Mi

The Nemu Nemu no Mi is a non-canon Paramecia-type Devil Fruit that grants the user the ability to make anyone fall asleep. It was eaten by Noko in the game only, while in the anime, the powers were attributed to the seahorse, who hypnotized Noko, but the fruit itself was never mentioned.

Strengths and Weaknesses
This fruit's main (and only) power, as demonstrated by Noko, can put an opponent to sleep through hypnosis. With the seahorse flute's power to manipulate memories, the fruit can become much more powerful. This power almost defeated the Straw Hat Pirates.

In the games, it was stated that to use this power, Noko must blow his flute to activate his powers, which is likewise similar to what is shown in the anime.

This fruit doesn't seem to have any specific weaknesses, aside from the standard Devil Fruit weaknesses.

Usage
Noko mainly uses this power to put his opponents to sleep.

Trivia

 * This is one of the three Devil Fruits that originates from video games, the other two being the Pasa Pasa no Mi and the Mini Mini no Mi. Unlike the other two, this is the only one to be adapted into the series (albeit in the non-canon anime, and only vaguely referenced).

Reference

 * A video showing the game where this Devil Fruit appears.
 * The full explanation of the fruits power in the game.