Elastic Search is excellent for those who want to implement a custom search engine.
Kafka is a powerful, reliable, and consistent distributed log. Kafka enables an application to support event sourcing, stream processing, website activity tracking (the reason it was originally built), and more advanced techniques required to be performant at scale.
GUIs I don’t shy away from software with GUIs and, just like my philosophy on multiple editors, I have GUI programs installed for things that I do in the command line. Sometime I like to visualise my git commits in a dedicated app, or use a GUI client for Postgres. For the way I work, they’re a “nice to have sometimes” and not “required”.
iOS A lot of the problem solving I do happens on my iPad, Apple Pencil, and Notes.app before a single line of code is written.