Ebony, Cocobolo, Lignum Vitae, Pink Ivory Wood, Purpleheart, Bubinga, African Blackwood, Kingwood, Snakewood, Leopardwood, Rosewood, Bloodwood, Teak....the list goes on and on.
I can think of SO Many suitable exotic hardwoods that are incredibly beautiful.
And then (of course) any of the softer woods that have been stabilized are also perfect for gun grips.
And the dyed laminated woods like Dymondwood are basically indestructible and very beautiful.
Walnut is a classic grip & gunstock wood but, it is actually fairly soft compared to the rarer exotics being used today.