Crysknife

A crysknife is a weapon that can only be produced by enchanting a worm tooth. It has a +3 to-hit bonus and does d10 damage against both small and large monsters, making it a nice choice for #twoweaponing. However, if it leaves your possession, it reverts back into a worm tooth (when fixed, this only happens 10% of the time).

The crysknives and the concept of worm teeth are from Frank Herbert's Dune.