A bō or kon, is a long staff, usually made of tapered hard wood, for example, white oak, bamboo and in some cases, for training purposes, rotan. Sometimes, it is made of metal or plated with metal for extra strength; also, a full-size bō is sometimes called a rokushakubō.
The bō is Donatello's weapon of choice.
The bo is a versatile weapon, able to defend as well as attack. Its length allows the user to keep enemies at a distance and twirling the staff quickly can block attacks.
This matches Donnie well, as he is more along the lines of defense and strategies more than offense. There's a running gag where his staff is easily destroyed by an enemy.
Don's bo has been modified to be able to project a blade, turning it into a Naginata, which is a kind of traditional JapaneseHalberd. The weapon has grip tape wrapped around the middle. Unfortunately, Don's bo easily breaks when used against Kraangdroids. In the episode "Metalhead", Donatello developed a robot to fight for him as he felt that his bo was inadequate against the alien technology they were currently facing, but came to accept his weapon of choice after he was able to defeat Metalhead when it fell under Kraang control (Although he attempted to turn his bo into a rocket launcher).
The Pulverizer once used the Bo-Staff to practice ninja moves, which he stunk at, until Donnie showed him some basics.
Mikey used the Bo-Staff when he was forced to poke Splinter with it while he was resting in "I, Monster", and managed to push the hidden button, sending the blade within inches of Splinter's face.
In the episode "Pulverizer Returns", Leo was forced to used the Bo-staff by Splinter to teach the turtles how to fight outside their elements. Leo would often trip over it though.
In the 2014 movieDonnie has a retractable spring loaded metal staff, which is much more resistant and stronger than its wooden version from previous incarnations. In the trailers Donnie uses it to reflect bullets, throw a car up in the air and push a container against Foot Soldiers. In the sequel movie, he has also added a taser to one end, allowing him to zap others with it and even use it to interface with plane controls.