Heretic888: "I haven't seen the video in question, but was this weapon a ninja-to or a shikomi-zue??"
Neither. The video showed the destruction sword and a shikomi zue - both straight blades - in addition to the "classic" ninjatou (shaped much like a katana - curve and everything - but with a shorter blade and longer handle, and a long saya to complete the illusion). All three were referred to as "ninja swords."
The feeling I got was that a ninja sword was not a particular item, but rather any sword used with ninja methods becomes a ninja sword.
Similar to my definition of ninja: ninja is as ninja does.