Bulk Rename Utility (Windows) is something I’ve been using for years to rename my music and video libraries in a uniform way. I usually just use it to rename seasons and episodes of shows incrementally, but it's capable of a lot more advanced rules.
It works well, does everything I ask of it, and it’s just totally free of bloat. Hasn’t changed in years in fact. Just does what it says on the tin. Renames your files in bulk.