I've committed "--i-meant-that" (for a destroy-the-remote-machine command that normally (without the arg) gives you a message and 10s to hit ^C if you're not sure, for some particularly impatient coworkers. Never ended up being used inappropriately, which is luck (but we never quantified how much luck :-)

I like the timer idea. I do something kinda similar by prompting the user to enter some short random code to continue.

I guess the goal for both is to give the user a chance to get out of autopilot, and avoid up-arrowing and re-executing.