Nunchaku

The nunchaku (or nunchucks as they are sometimes referred to on the show), is a weapon that consists of two sticks connected at their ends by a short chain or a length of rope. The word itself comes from nun (ヌン), meaning "twin" and shaku (尺), the approximate length of each arm of the nunchaku.

It is notable in the TMNT universe as being the main weapon of choice of Michelangelo, although a few characters throughout the franchise have been seen wielding them as well.

Trivia

 * Broadcasts of characters wielding nunchucks were censored on UK television during the 1990s, often causing Michelangelo to either go bare-fisted during fights or wield alternative weapons. Eventually, this led to him using a new grappling-hook like weapon called the "Turtle Line" later on in the 1987 series.

Links
Wikipedia's article on nunchucks.