Simply put, I will be adding this plugin to my list of other boilerplate plugins that I use for every WordPress site.
Because this plugin allows you to visually choose which images should be included when inserting a gallery.
WordPress already has the ability to manage the images that appear in a gallery (include or exclude), however it requires you to seek out the IDs of these images and then add an attribute to the shortcode with a comma separate list of these IDs. It's extremely unfriendly.
Although this plugin hasn't been updated since June 2011 at the time of this writing, which was an immediate red flag for me, I gave it a shot and it seems to work perfectly.
Thank you, author!