My daily use case is basically for an office suite. With ancient tools like grep, awk, and sed, plus a bit of scripting, I've been able to automate a lot of tasks.

I have scripts that do everything from converting odts etc to pdf while watermarking them and adding dates etc to the file names for delivery to clients, to scripts that can produce client documents from a csv file containing client information. I also have a cron tasks that finds new files each night and converts them to a hidden text file (with a custom extension to differentiate them from regular txt files), so I can quickly grep my entire file system.

I also have a script that unzips odt files and edits the xml data and then repackages them, so I don't have to open 10 documents in writer when there's a bunch of documents that need the same edit.