I'm a huge fan of wood handles, especially darker colored and more reddish wood with a lot of texture like Ironwood, Mahagony, Cocobola, Rosewood, Teak, maybe Walnut.
A good texture is important as well: Swirls, or even better: stripes.
I don't really like the lighter colors with a greenish touch like olive wood
Wood is warm, light and gives a good grip. Combined with a butt cap for protection a knife like this is a pleasure to use.
In the EDO Photo Contest, Peter Kaufman had shown us some top examples in his "Randall Ironwood Forest"