Here are some links to my presentation of Buy What You Use, Use What You Buy from Macstock 2018, including audience-suggested items.
List of iOS apps - Settings>General>iPhone Storage
KB Covers Keyboard Overlays (one example - there are many companies producing them)
KeyCue by Ergonis Software
Default Folder X by St. Clair Software
LaunchBar by Objective Development
CamelCamelCamel price tracker
TPG To Go - app to determine which credit card gives you the best deal on a given purchase.