Nanashaku Jitte

The Nanashaku Jitte is Smoker's primary weapon. The tip of the stick is made of Kairoseki, which Smoker uses to suppress Devil Fruit users' powers in order to capture them. The weapon was effortlessly destroyed when Boa Hancock kicked it after its petrification, causing it to crumble in pieces.

Abilities
As the jitte is tipped with Kairoseki, it can be used to nullify Devil Fruit powers simply by contact. Smoker uses this to his advantage to strike such opponents, as well as to stop them by sapping them of their powers and mobility. He uses it in conjuncture with his Moku Moku no Mi powers to get close to his opponents in order to make his strike land. Because of its composition, the jitte does not transform into smoke along with Smoker.

Trivia

 * The jitte (also known as a jutte, both meaning "Ten Hand") is a weapon used by Japanese law enforcers, which fits Smoker's status as a Marine officer perfectly.
 * A shaku is a measurement unit in Japan, one shaku being 10/33 meters. Based on the name (seven shaku), the jitte is 2.12 meters in length.