In Exalted, daiklave is the Old Realm word for "Huge Magical Sword". They're magical weapons, usually made out of one of the Five Magical Materials: Jade, Orichalcum, Moonsilver, Starmetal, or Soulsteel.
In addition to being unbreakable by any normal means, daiklaves (and similar magic weapons) tend to be large; they're too heavy to use without the use of Essence, which makes them as light and as easy to use as their mundane counterparts.
They also tend to be highly conspicuous, due to their size and value. Wearing a daiklave in public announces that you're a potentially dangerous magical being. This is fine for the Dragon-Blooded, but can be a serious problem for other Exalted trying to keep a low profile.