By far my fav is bone. I do have a little stash of MOP and some silver sheets that I am patiently waiting to make a set of scales with. I have done a few MOP repairs but never a full set of scales.
G-10 is terrible stuff as far as dust and toxins are concerned, but it does make really nice liners. I think it is better as a liner than a scale material.
Horn was my go to for a long time. I still like it, and I think it is wonderful to work with and beautiful.
For the most part I am not a big fan of the acrylics and polycarbonates. I do have a set of wood and acrylic slabs that are destined to be something special. I have not found exactly the right razor.
There are certain materials that I feel are better suited for some blades than others. An old Sheffield looks really off in a set of loud coloured plastic scales. That is sort of where picking the right material for the right blade comes in. That is all about personal taste though.