The Kame Kame no Mi is a Zoan-type Devil Fruit that allows the user to become a turtle hybrid and full turtle at will. It was eaten by Pekoms. Its powers were first revealed in the Fish-Man Island Arc, but the name of the fruit was not given until the Zou Arc.
The main strength this fruit grants is the ability to transform into a turtle, in which forms a protective shell that is as hard as diamond. The shell can guard against things such as bullets and collapsing buildings without any signs of damage. No weaknesses are currently known, other than that the user is affected by the standard Devil Fruit weaknesses.
Pekoms transforms into a turtle when he comes under attack in order to shield himself. However, when he transforms his clothes slip off due to his body entering a shell, forcing him to fit them back on when he transforms back. He was also quick enough to activate his ability in time to block a majority of gunshots from Capone Bege's attacks.
The Kame Kame no Mi is the first canon Zoan Devil Fruit to be introduced after the timeskip.
With the exception of the Tama Tama no Mi whose classification is unknown, the Kame Kame no Mi was the only Devil Fruit within Big Mom's crew that was not a Paramecia.