One of the git commands that has saved me a few times is git reflog. This will give you a reference log of actions you've recently completed. If you've lost a local commit (maybe you accidentally reset your local branch to the remote), this can be a useful command to retrieve it.
This week I needed to re-apply an old commit from a couple of weeks ago. I didn't fancy trawling through hundreds of lines of the reflog, so I figured it would be easier to achieve with grep. However, I actually discovered that the functionality I needed is built into git itself. TIL:
git reflog --grep-reflog <pattern>
This will search your git reflog for commit messages matching <pattern>. The pattern is a regular expression, so you can search for a word/phrase or some other pattern if you need.
This saved me a bunch of time, and thanks to a quick search I added a new trick to my toolkit. I also found the old commit with a single command!