Jess

Thumbnail Updater does exactly what it’s name implies: it updates thumbnails. WordPress 2.9 introduced support for 
post thumbnails but one problem is that the support is not backwards compatible—meaning that if you downloaded or created 
a theme that supports post thumbnails, any images uploaded prior to the activation of that theme will not have the new thumbnail size.

Thumbnail Updater

A plugin for updating your thumbnails whenever a new thumbnail size is added with add_image_size()

Volkmar Kantor

The plugin provides the functionality to adjust the crop region of cropped images. It add buttons to the edit-pages and media-dialog to access a crop-editor. 
In the crop-editor you can choose one or more (if they have the same ratio) imagesizes and cut-off the part of the image you want.
The plugin is especially useful for theme developers who want to keep full control over cropped image sizes. If you want to dive even deeper, you can get informations about the hooks and filters on the <a href="https://github.com/vollyimnetz/crop-thumbnails" rel="nofollow ugc">github page of the plugin</a>.

Crop-Thumbnails

Amazing work on this plugin. It make developers and users life easier creating a handy-way to crop thumbnails in the used sizes across the site.

Where's the button "This plugin should be native"?

"Crop Thumbnails" made it easy to get exacly that specific image-detail you want to show in your featured image or gallery image.

Thumbnail Updater vs Crop-Thumbnails