Trapdoors and doors. With the number of varieties of wood, there are a lot of colors to use and their <1 block thickness and, for some, transparency gives a great way to add depth to a surface.

Structural: cobble/deepslate

Decorative: Block of Lapiz

Hot take: The nether woods. They seem crazy, but the colors work in a remarkable number of situations.

But I love working with wool. Some don’t like the texture, but I think it works really well.