Mechanic

We’ve replaced several apps with just this one!
I've used Mechanic for about a year now. Their huge library of pre-built tasks made it easy to get started auto-tagging customers or orders, scheduling product publishing, sending notifications for big orders. Setup was easy.
When I needed something custom (a complex order hold and release workflow), I was easily able to learn enough Liquid to modify an existing task to achieve what I wanted. The documentation is good, and their Slack community is also super helpful.
If you've ever thought "I wish Shopify could just do X automatically," this is probably your answer.