Balisong

A balisong (also butterfly knife or fan knife) is a folding pocket knife with two handles counter-rotating around the tang such that, when closed, the blade is concealed within grooves in the handles. It originates in the Philippines (particularly Batangas), but this design has been widely exported since its inception.

Appearances:
 * In possibly the most unusual instance of balisong use in existing fiction, a giant two-handed sword version of the balisong (known as the "Damascus Blade") is used by the title character of the manga series Battle Angel and its sequel Battle Angel: Last Order. Due to the popularity of this series, physical replicas of this oversize balisong actually exist on the open market, reaching a whopping 37 3/4" in length when unfolded (triple normal size). The portmanteau balisword has been coined to describe the generic form of this weapon.