I've gone through numerous faves over time, but right now I'm at:
Synthetic - G10
Natural - stag
G10 sort of speaks for itself: durable, weatherproof, endless colors/color combos, can be glassy smooth or very aggressively textured to suit tastes and uses, etc.
As for stag, I love the way it looks and feels, and I like that it can be had without sacrificing a whole animal, as it is easily available in the form of sheds. I'm not against hunting or commercial processing of animals for food, etc, I just think it's cool that something an animal sheds naturally every year can be found and recycled by man for other purposes. :thumbup: