I only buy Mammoth if we're talking ivory. They're already dead, so it doesn't matter to take that. But I don't want to kill Elephants, I like them! 
Personally, I prefer bone or horn. Antler is good too.
My personal favorite is actually buffalo horn, with elk antler a second and sheep horn a third.

Personally, I prefer bone or horn. Antler is good too.
My personal favorite is actually buffalo horn, with elk antler a second and sheep horn a third.