Dib'Muad's Crysknife

Dib'Muad's Crysknife is a rare-quality dagger, primarily intended for rogues.

Source
This is one of three quest rewards available after completing The Big Bone Worm in the Bone Wastes of Terokkar Forest.

Trivia
Along with the Jom Gabbar, this is an obvious reference to Frank Herbert's Dune; "Dib'Muad" is a reversal of "Muad'Dib", the Fremen name of Paul Atreides, and a crysknife is a Fremen weapon created from the tooth of one of the sandworms of Arrakis.