The Katana is a long, single-edged, curved sword indigenous to Japan. It is the best-known Asian weapon, and one of the two best-known sword types (the other being the European broadsword). It was historically used by the Samurai warriors, along with the shorter Wakizashi. The two swords together are generally referred to as a daisho. Unknown to most laypeople (and countless film directors), the katana and wakizashi were normally worn with civilian dress, and were carried as peacetime weapons. Another daisho, consisting of the Tachi and shorter Tanto, were worn with armor. An easy method of differentiating the two is to check the lengths -- while the katana and tachi are roughly equal in length, the tanto is much shorter than the wakizashi. Also, the katana and wakizashi were worn edge-up, while the tachi and tanto were worn edge down.
In X-Men Origins: Wolverine, Wade Wilson dual-wields katana, using them to deflect bullets fired by African diamond smugglers. At one point, he slices an oncoming bullet into two halves that continue past him and kill the two gunmen behind him.