I like them all. Wood is very nice. I love the burls and the stripped grain woods. I like stag. Stag can be great or bad; it is not consistent enough to be my favorite. Bone properly done is fantastic, but again not all bone is done well. However, there a multitudes of variations on colors and jigging; you can find something that will strike your fancy. I like micarta quite a lot, but it lacks character sometimes. But it is a pretty consistent material. Stone, is pretty, but fragile and heavy. Various ivories are beautiful, but expensive.
So, for me, I generally take up with wood or bone. I will pick up a stag handled knife on occasion because it is such a nice material. My customs both have micarta.
Edit:
I had to come back here and make mention of the fact that I am really fond of pearl and abalone. I have several knives in these shells and I just love them. I only use a couple with any regularity as shell chips easily and the older I get, the droppier I get.
Ed J