Here are some relatively unusual bash use cases that I've ended up relying on. I'm trying to list them in the order of how necessary they are in my daily bash use.
Constant work in progress as you never stop learning. Sources hopefully at the bottom.
Simply hit Ctrl+r to search through your history for a previously entered command.
I believe these are called emacs mode, either way I've used them since I was a teenager and they're still used daily.
$ printf '%(%Y%m%d.%H%M%S.%s)T\n' 20180206.113447.1517913287
$ printf -v mydate '%(%Y%m%d.%H%M%S.%s)T\n' $ echo $mydate 20180206.113529.1517913329
Just search for
Parameter Expansion in the manual, it's all good.
For example loop the output of a command line for line.
while read -r line; do echo "$line"; done < <(grep -v 'nothing' /etc/file.cfg)
Run a command with
\ls to bypass any aliases called ls.