Like Spotlight for Experts
EasyFind
Spotlight is great, but sometimes you need something more specialized. EasyFind finds files and folders by name, content, tags, or comments using advanced Boolean operators similar to DEVONthink and DEVONagent, wildcards, phrases, even regular expressions. It does not require indexing, is fast, and uses very little memory.

Of course EasyFind doesn’t just give you the files. It also shows previews and offers many other options to work with them.
Version 5.0.2. Requires OS X El Capitan or later.
Photos and Webcams on Your Desktop
PhotoStickies
With PhotoStickies you have your dearest ones always with you at your Mac. Or at least pictures of them. PhotoStickies shows your favorite pictures directly on your desktop, floating and, if you like, borderless.

PhotoStickies also shows video streams from cameras or live webcams on your desktop and updates them automatically. You can even record them or make them your desktop picture.
Version 6.0.1. Requires OS X El Capitan or later.
Honey, I Have Shrunk the Images
ThumbsUp
Create thumbnails for your website in seconds with ThumbsUp. Drag them to its icon and it converts them in a batch with the previously set options. Of course ThumbsUp works with all image formats supported by the Mac including PDF documents and movies.

Version 4.5.3. Requires OS X Yosemite or later.
Little Menus with a Big Effect
XMenu
Add one or more out of six menus to the right side of your menu bar. They give you access to your applications, folders, documents, files, and text snippets. Launch any app with a single menu choice or insert text snippets into your documents.

Version 1.9.11. Requires OS X El Capitan or later.