180mm Tojiro Aogami (blue) steel deba (butcher's) knife. This knife comes in at 309 grams, plenty of weight to help you get through those tough bones, or fish head that you've been struggling with.
The knife is only sharpened on one side, in traditional Japanese style. This type of blade profile allows for a more acute edge than the traditional 50/50 grind found on most knifes.
Aogami (blue) steel is able to hold an edge better than almost any steel available today. Prized for its toughness, is also has a great ability to take an edge and keep it. The steel is slightly reactive, although the cladding from the factory should make any rust issues a non-issue.