The Hane Hane no Mi is a Paramecia-type Devil Fruit that allows the user to transform parts of their body into large fan-like propellers. It was eaten by Faron, a member of the Revolutionaries, making her a "Fan-human."
The main strength of the fruit is that their body parts literally get turned into large propellers, giving them a significant ability to cut through objects with the grinding blades and the ability to also push objects with the powerful wind produced by it. They can also propel objects through water by using their propellers as momentum.
Faron uses it in order to propel a water craft through water in the Calm Belt, albeit very slowly and cautiously as not to alert the numerous Sea Kings lurking beneath the waters. She can use it as a fan to blast objects away, carry her and one other person over short distances and also use it as a weapon to dice and cut up her enemies.