Handle material is more of a personal choice, since all have their plusses and minuses. I prefer wood for the look, and walnut in particular because its tough, easy to work with, and the grain provides a nice grip. I recomend though, if you don't want any moisture to be absorbed, that you first treat the finished handle with oil, then seal it with polyurethane when its "dry" and clean. A couple of thick coats should provide all the protection from water and oil you could need, and provides a nice grip to boot.