Sharp Edged Recurved Toki
I am on a bit of a mission to develop my toki designs at the moment. I love the shape of the old tokis that were used for practical work by pre european Maori. I try to incorporate as much of this design as I can in my Hei Toki pendants.
The important part of a functional toki is the cutting edge at the bottom. I am no expert in crafting or using functional tokis, I just like to try and replicate some of the aesthetics to give the impression that a Hei Toki could actually be used. Having well defined edges and corners on the cutting edge is something I always try to include, there is a point (especially with fine grained stone) that is can be too sharp I am sure.
The key feature of this design for me is the inward curve obove the cutting face. This draws attention to the main event of a toki, the cutting edge. It is important for a practical toki to have a shaped back side, if this were flat then the tool would not be very effective. 
This stone is a deep green and has a wonderful translucency to it which comes through near the cutting edge and you can see right into the stone.
