Shiro Shiro no Mi

The Shiro Shiro no Mi is a Paramecia-type Devil Fruit that allows the user to become a living fortress, making the user a Castle Human. "Shiro" (城) is a Japanese term for "castle". It was eaten by Capone Bege. It's powers were first revealed in the Sabaody Archipelago Arc, but the name of the fruit wasn't given until the Zou Arc.

Strengths and Weaknesses
The main strength of this fruit is that it allows the user to become a living fortress, the inside of their body holding many cannon ports and drawbridges, and stone brick rooms. The user can hold even living people inside their body, by shrinking their sizes as long as they are within a vicinity within the user. When the objects and people within the user reach a certain distance away from the body, shown by a pinkish layer of an unknown aura centered on the user's location, they revert to full size.

He can also use his body as a storage facility as he is shown to house food and drink for his men and any outsiders. This has the advantage of lulling others into a false sense of security who think they are facing a single individual in combat who appears to be lacking armaments on the surface, only for the fruit's user to reveal the militias and weaponry hidden within.

While people are inside him, he seems to also make a miniature version of himself as a way to communicate with those inside, however, being in his own body, he can still just talk and they would be able to hear him.

Should the user be inhaling smoke or any similar substances, the insides would be filled with it as well, as when Capone was smoking a cigar, the soldiers inside were suffering from cigar smokes. It seems that when the user is inside the fortress, his body becomes idle. Other than that, the user is also weak to the standard Devil Fruit weaknesses.

Usage
You guys have already lost... in sheer military force. Capone Bege primarily uses his ability to launch a powerful surprise attack against unsuspecting adversaries. Holding his entire crew within his own body, they can fire guns or launch cannon blasts from his body, which would return to full size once leaving the boundary of Bege's ability. The troops can also rush outside of their captain's body via horses to overrun and surround their enemies. All of this results in bullets, large cannon volleys and cavalry seemingly popping out of nowhere from one man.

Bege also uses this ability to provide a place for him to have private conversations with other people.