The Last Service Account Key
$ git log --all --oneline -- '**/service-account.json' | wc -l
47
$ git log --all --oneline -- '**/service-account.json' | head -1
a3f8c2e delete: remove production service account key
That commit sits in your history like a monument. Not because of what it added, but because of what it finally took away. Forty-seven commits that existed only to move secrets around, rotate them, revoke them, apologize for them, and eventually eliminate them.
That last deletion was the sound of the door closing on an entire class of infrastructure vulnerability.