How about a commit hook that warns when it looks like you're about to commit a secret key?
Not bad in itself, sometimes all you need is a dirty script, but as other have said, they tend to stick around, a key part of our CI module is actually putting expire date on scripts, or check dates. I will receive an email telling me to check and a warning on the CI at build time. It's been great to keep our code clean while allowing us to still do things dirty when required.