水野史土

This plugin shows post/page/category/tag/comment/media/user IDs on admin’s edit post/page/category/tag/comment/media/user pages. You can see the ID when you visit an edit post/page/category/tag/comment/media/user page. 
Since this plugin hooks on ‘edit’ link, only users with priviledges can see IDs. For example, a user of author role can see post IDs, while a user of subscriber role cannot.
You can find a brief description in Japanese on a book <a href="https://php4wordpress.calculator.jp/" rel="nofollow ugc">Introduction to PHP for WordPress Users.</a> (written in Japanese.)

ShowID for Post/Page/Category/Tag/Comment

This plugin shows post/page/category/tag/comment/media/user IDs on admin's edit post/page/category/tag/comment/media/user pages.

Aaron T. Grogg

This plug-in limits the classes WordPress added to navigation menus to only those desired by the Theme owner, 
adds a unique ID to each <code>li</code> and removes any empty <code>class</code> attributes.
More about this plug-in can be found at: 
http://aarontgrogg.com/2011/09/28/wordpress-plug-in-navigation-menu-ids-classes/
Please let me know if you have any questions/suggestions/thoughts,
Atg

Navigation Menu IDs & Classes

At least some aspect of this plugin seems like it should be available in WordPress core. 
I understand the rationale for menu items having menu-item-ID, but it's pretty practical for them to have the slug in there, as this plugin provides.
Suggestion for plugin feature - offer option for slug prefix.
Like if I have a menu item "updates" I may use the class "updates" elsewhere, but class "menu-item-updates" would target the menu-item for sure. Of course I can currently use double selectors.



1 for inclusion in core

To reduce the extraneous WordPress classes and add unique IDs to navigation menus.

ShowID for Post/Page/Category/Tag/Comment vs Navigation Menu IDs & Classes