Krys knife
From Dune2k.com Wiki
The culturally important Fremen's knife, formed form a worm's teeth.
Possible origin: Keris" means "small dagger" in Malay. It is considered as the world top-blade for stabbing (rather than slashing), with its specific design including a large base and a waved large blade. Each blade was said to have its own personality, with its attached spirituality and magic.
