[aappleby]

What if the tool required an "un-safeword" to do destructive things?

"Do you really want to 'rm -rf /'? Type 'fiberglass' to proceed."

[jabroni_salad]

There is a package called molly-guard that makes you type the computer's hostname when you are trying to do a shutdown or restart. I love it.

[nthdeui]

Like tarsnap's --nuke command:

  --nuke  Delete all of the archives stored.  To protect against accidental
          data loss, tarsnap will ask you to type the text "No Tomorrow"
          when using the --nuke command.

[drougge]

Probably inspired by Vinum's "NO FUTURE" for destructive operations. (Vinum was a raid system used on older versions of FreeBSD.)