I haven't stayed at a job for longer than 3 years, and all of them have been internal projects with no external visibility, so I can't really know for sure. I do have a 21-line python script that I still use which I initially committed to github in 2008, so that's certainly a contender (first internship started in fall 2004).
And of course, reading that, I see my script is hugely overkill since all it does is alter the default port and allow you to pass one in -- something the one-liner can apparently do. Oh well.
The script is an expansion on the web server one-liner: https://github.com/imnotpete/odds-and-ends/blob/master/pytho...
edit: the one liner: http://www.garyrobinson.net/2004/03/one_line_python.html
And of course, reading that, I see my script is hugely overkill since all it does is alter the default port and allow you to pass one in -- something the one-liner can apparently do. Oh well.