LordPretender

This plugin allow you to add files into your media library without having to upload them. So, you will be able to share, for example, your files into your Google Drive. 
This also save you steps to download the image to local computer and upload again to your own WordPress.
<h4>Features</h4>
<ul>
<li>Automatically downloads and adds the file to the media library.</li>
<li>After the uploading is successful, you are redirected to the edit screen</li>
<li>A new dropdown list is available in the media library to let you display only uploaded files, not uploaded files, …</li>
</ul>

Add Media from URL

large chunks of code taken from the much better original here:

https://en-au.wordpress.org/plugins/lh-add-media-from-url/

IMO it unethical to use this plugin

A crappy clone of the original

Let you add media files into your media library without having to upload them.

shawfactor

This plugin allows you to create duplicate images in the media library, rather than having to create a new copy of the image and upload it to WordPress again.
It works by copying the post and its metadata into a totally new file in the media manager. Any changes you make to the new copy of the attachment — updating the caption or cropping, for example, will only be applied to the new attachment, not to the original.
This is useful if you want to edit or crop an existing image without effecting the original
To use, go to the Library tab and you will see a copy file link below each media (this will only appear in list view, see faq)

LH Copy Media File

Thanks! It does what it's supposed to do.

Great plugin! Does what it's supposed to.

Allows you to create duplicate images in the media library.

Add Media from URL vs LH Copy Media File