Taxonomy Templates allows user selection of a theme’s available taxonomy templates, much like how pages can select their template. If you’ve ever wanted to style many categories differently, it can quickly get tedious making copies of templates and changing file names to match slugs or id’s. Lacking a term meta data store, this plugin stores the selected templates in the options table.

With the plugin installed, and available templates in the theme, the user can select the desired template on the Edit Category/Tag/Taxonomy page:

On the theme side a comment is added to the top of the template to identify it:

 Taxonomy Template Name: SMPR

UPDATE: Now available in plugin repository