Calm-Calm Fruit, or Nagi Nagi no Mi, is also one of these Devil Fruit with annoyingly specific usabilities. All it does is shutting off the noises within the bubble it creates. Yes, it could prove helpful in stealth and infiltrating missions, but that's the extent of it.
As a Devil Fruit that has shown no clear weakness, the Magu Magu no Mi is perhaps one of the strongest.
