If we exclude smaller scripts then one thing that stands out is a small CLI application (written in nodeJS) which takes all emails from Gmail marked with a spec

If we exclude smaller scripts then one thing that stands out is a small CLI application (written in nodeJS) which takes all emails from Gmail marked with a special label and uploads their attachments to special Dropbox folder for my company accountant. So forwarding invoices to my accountant is as easy as throwing a special label onto the email and boom, done. Was totally worth automating, been using it for like two years now.