Then there is also what you have to do at work. In a former job, I had to use the ".pl" extension because a higher-up saw it in a URL and asked what it stood for. "Perl script", I said, being the only Perl programmer there, and lo, another carefully-thought-out standard was rammed down everyone's throat by a PHB who knew as much about logic and process as a mound of live bait.

Personally, I like ending them in ".ksh" and watching people's faces when they see regular expressions for the first time. Evil, but in a good way.