Clients have requested the ability to create a custom field that works like the 'Tags' field, but has its own pool of tags, rather than using the global tag set that all the Tags fields use. This would allow users to curate a smaller set of tags for a specific purpose, that would autocomplete as users started to type in this field. Should allow multiple tags and otherwise operate just as tags fields do currently, but should not share autocomplete values with the rest of the tags fields.
Click 'Me Too!' to vote up this feature, and add any additional thoughts or use cases in the comments.