markenzeichen

This simple plugin – which is also WordPress network compatible – automatically redirects 404 errors to the best matching and existing content in your WordPress blog. 
The matching is based on the slug of the content not found and searches also on taxonomy pages (tags & categories). This is perfect when you have changed the permalink settings of your taxonomies. 
All redirects are permanent (301) which is a SEO best practice. 
Since this plugin doesn’t need any configuration it works perfect in WordPress Network / multisite setup.

404 ReDirector

Simple, SEO friendly, permanent (301) and automatic redirect of 404 errors.

featurenotabug.

It can be quite annoying when you want to delete a post but it only has a Trash link. You then need to go into the trash to delete it for real. This plugin allows you to delete a post permanently by turning the trash links into a permanent delete link when you hold down the Esc key on your keyboard.
Maybe Perma Delete adds a convenient way to permanently delete content directly from the admin without the risk of pressing it accidentally:
<ul>
<li>Esc-hover in post tables: Hold the Esc key while hovering over the Trash action in post, page, or custom post type lists. The link will change to Delete permanently for that specific row.</li>
<li>Esc-hover on the post edit screen: On the single post edit screen, hold Esc while hovering over the Move to Trash link to turn it into Delete permanently.</li>
<li>Bulk actions: The bulk actions dropdowns always include a Delete permanently option alongside the default Trash action.</li>
</ul>

Maybe Perma Delete

Hold the Esc key to get the option to permanently delete posts, pages, and other content, instead of moving them to the trash first.

404 ReDirector vs Maybe Perma Delete