I want to thank all of you for taking the time to give such informative answers to my question. I'm looking forward to researching some of the woods that you have mentioned, and will do my best to not impact sensitive ecosystems if that is possible (it is hard to imagine using any wood without some impact somewhere).
The bokken that I use (the one that I am making is for my wife who has had to stop aikido for the next couple of months until our twins are born) is hickory (Bujin) and has stood up to several years of use nicely, but it is difficult to get hickory of that quality. I'll look into the high impact hickory that has been brought up. I have used purpleheart in a few projects recently and enjoyed the feel of working it, so it is good to hear that it holds up well to use. I'll look into some of the more exotic woods that you all have mentioned, they sound very interesting.
Again, many thanks for taking the time to help me out!