This is a list of some of the iOS Apps that I use that are actually useful and become even more powerful when combined with the Workflow app.
Apps that support X-URL-Callback or a at least a URL Shem.
Pythonista write and execute Python scripts right on iOS.
Today helps build and keep track of your habits.
WaterMinder keep track of your daily water intake.
RemoteBoot WOL start a computer via “wake on lan”.
Anki a great flashcard app.
Things a todo list app thats better than apples native one.
you can find some more on the following links they might however not be as useful.
Apps with Siri shortcuts (for the Siri Shortcut app).
None yet. We will see the first once as iOS 12 comes out.