I usually recommend one of the three following materials for a working knife handle: They are Micarta, Stabilized Wood and Desert Ironwood. Micarta is an electrical insulating material made from layers of linen cloth or paper laminated together under heat and pressure. It has high strength and is sometimes referred to as the steel of the plastics industry.
G10 is made up of laminated glass fiber and resin and is available in many colors.
Stabilized Wood is similar to Micarta in that it is injected with resin under vacuum and then cured under pressure. The result is the feel and look of natural wood but the stability of a plastic.
Desert Ironwood is a material made by nature for knife handles. It is very dense and oily, almost waxy, very dark brown with gold streaks running through it. It is becoming a rare hardwood and comes from the Sonoran Desert in Arizona and Mexico. It is the most stable of all hardwoods and is well suited to the extremes of salt water and the high mountain range environments.
Stabilized Maple Burl, or Fiddle Back Maple can be dyed many colors. I like to combine the stabilized woods and or G10 with desert ironwood in a multi piece handle. Various G10 spacers can be added for contrast. The result is a striking effect that is durable and has the appeal of a natural material.
Animal materials like Stag, Ivory, and Ossic make beautiful handles but should be considered only if the user is prepared to give the knife extra special care.