Although I can add any handle material you specify to your custom-made knife (see the handle above made from mammoth molar), this page shows the materials I commonly use.
I stabilise the wood if it has an open-grain character to protect it from moisture. However, some woods - African blackwood, pink ivory - are so tightly grained they don’t need it.
Some of my hand made knives use synthetic materials; this makes the knife dishwasher safe.