I think it would be cool if K2 added a "Featured" parameter to the category and tag menu options.

Any thoughts?

You mean like the items have?
What purpose would that serve, content-wise that is.

It would provide the ability to display a list of only featured items (for category or tag list pages)

/blog
/blog-featured

tag/joomla-extensions
tag/joomla-extensions-featured

Keep in mind the "featured" label can be used to denote various content classifications:

- New
- Sale
- Discounted
- Coming Soon
- Editor's Choice

I think a plugin or extrafields (think v3 extrafields) can tackle this issue better.

Adding checkbox and checking in your template of that value can print extra markup. images etc...

How would one use a Yes/No checkbox extra field to display certain ("featured") items? I'm not following what would need to happen in a template. I had not previously used extra fields but I did create a group, plus an extra field drop-down with yes/no options but I'm not sure how to modify the template code to get at that field as an option for a menu item. I modify the template with an override and then use that template for this one item? Where might I find an example of the code to copy? My searching isn't turning up anything useful. Maybe I am misunderstanding your answer to the OP's question (which is also mine.)

I searched and found several questions to my question of how to display only featured items in a menu item. I did see that I can set up a multiple-categories menu item (even though my featured items may only be in one single category) and then display only featured items, and it works, but for this particular menu item I want no "chrome" whatsoever (ratings, author, publish date, etc.) and tweaking the category display options to suit just this one "featured" menu item throws off the desired display of this category's items (featured or non-featured) in other menu items where I want some of that chrome to appear.

Thanks,
~J

In the category's settings you can choose to show or hide only featured items and you can show the featured items on top.

If you are using a multi category menu, these same settings in the menu item's parameters.