My grandfather recently passed away and looking in his office I found this knife/shank. My grandmother said that my grandfather's uncle gave it to him when he got back from WW2. I know it might be a long shot but does anyone have any idea where this could have come from? She says that it was taken from an enemy soldier.
This has the appearance of being folk art. I don't recognize it, but if your relative fought in the Pacific, I would suspect it came from one of the islands - and not from a Japanese soldier (unless it was taken from someone who had in turn taken it from an islander). That said - and understanding that I do not recognize it), you might find someone who has the right ethnographic background in /r/askanthropology. Perhaps someone there will recognize the art work.
Kinda looks like a kukri, but seems a little more whimsical than the examples. http://en.wikipedia.org/wiki/Kukri