Not all of my plugin experiments are succesful but these plugins in particular seem to be doing alright. They are free to use. My most recent contribution is the Gutenberg Prototype.
Attachment Slugs for WordPress
Enables you to add permalink support for media attachments making the attachment URLs more friendly and great for SEO results.
Run beta or release candidate versions of Gutenberg from GitHub. This is perfect for developers building blocks for the new WordPress editor.
Users by Date Registered
This simple plugin allows you to filter your users by date registered and a new column is added to the users table displaying the date the user registered on your site.