I have used black walnut pellets on pork butts in my MAK. I would classify it as a "hickory heavy" flavor compared to straight hickory and then there is pecan, which I call "hickory light". If you are looking for a heavy wood taste when you use it to smoke
something, be prepared for the heavier taste. I actually liked the results.
Try some at the beginning of your cook and then shift over to hickory or pecan. I think you will find the flavor like no other.
I am hoarding the remainder of my black walnut pellets for another cook one of these days.
Art