Hiruko

is a puppet used by the Akatsuki shinobi, Sasori. As a puppet, he served as Sasori's "puppet armour", as Sasori was capable of hiding inside of it. Sasori even adorned Hiruko with the Akatsuki's robes, and hid inside it so often that others came to recognise him only when he was wearing it. In the anime, Hiruko is a human puppet made from the corpse of a renowned shinobi. According to Chiyo, Hiruko was Sasori's favourite puppet.

Abilities and Weapons
A puppeteer is, under normal circumstances, at a disadvantage in close combat, as their enemies slip past their puppets and attacking the rather defenseless user directly. Hiruko was an innovative method created by Sasori to circumvent that weakness, with the puppet becoming both armour and weapon.

All weapons installed in Hiruko were coated in Sasori's special brand of poison, which would kill the victim after three days of painful paralysis.
 * Extendible iron tail provided offence by stabbing and defence by rotating around the body.
 * Heavy back shell for additional defence. A new addition since Chiyo last saw it twenty years ago.
 * Rapid launching of senbon from the mouth.
 * Torpedo-shaped left arm that launches shrapnel of senbon in all directions. A new addition since Chiyo last saw it twenty years ago.
 * Granted Sasori a gruffer voice.

Trivia

 * can be translated to "leech child".
 * Hiruko is a Japanese Fisherman god. It can also be translated into "Ebisu".
 * Hiruko's tail was seen in a flashback of Sasori's childhoods as a part of an unfinished puppet. It had a split end.
 * Hiruko was erroneously called Sasori's eighteenth puppet in the anime. This was because literally translates to "number eighteen".
 * Both the puppet Hiruko and the Third Kazekage were stated to be Sasori's favourite.