Horse Stall Mat
Made from recycled tires, this rubber mat is 99.5% black with light flecks of white, red and gray rubber mixed in. It is very dense, tough material. It is made for horses to stand on all day so it has to be tough. A 12"x12" square weighs 4.5lbs!
Grind this just like wood for your handles and you will have a strong, slip resistant cushioned handle like no other. This is the hottest handle material out there right now for hard use knife handles.
Use pins like you would with wood or other material and contact cement to bond it to the handle.