What are your least used blocks when building?

Whether it's creative or survival, what blocks do you use the least when building? Are there any blocks (preferably full solid blocks) that you don't use at all? Whether it's because you dislike the appearance, or just don't have a use for it.

One that came to mind for me while writing this is glazed terracotta. Rarely used, and when it IS used, it's always in niche areas.

Asking this as I'm trying to recreate buildings from real life, so I need to create a resource pack for custom textures (which will replace the original blocks).