Code that will only execute once Goal

The goal of this challenge is to write code that will execute once and only once.  This means basically that it damages the program, script, or environment in some way.  If rebooting the system allows the code to run again that is permitted.

Scoring

Number of votes.  All assumptions must be clearly listed.  Any answers just initiating a reboot or halt will be disqualified.

Additional Rules because Greg Hewgill is a demi-god

No root access is permitted.

End Date

The contest will close on May 31, 2014.

Edit

This contest has been changed to popularity contest.
Vigil
Finally a usecase for Vigil!
def main():
  raise Exception()

Excerpt from the &quot;language specification&quot;:

It goes without saying that any function that throws an exception which isn't caught is wrong and must be punished.
...
If an oath is broken, the offending function [...] will be duly punished.
How?
Simple: it will be deleted from your source code.
The only way to ensure your program meets its requirements to absolutely forbid code that fails to do so. With Vigil, it will do this for you automatically.

There are other ways to do this, because Vigil provides the keywords implore and swear which are basically oaths to adhere to certain pre- and post-conditions:
def main():
  swear 0 &gt; 1