Cog, my templating and code generation tool, seems to be like the little engine that could. I wrote it years ago to bring a little Python power to a non-Python job. But then it was unexpectedly useful while preparing my slides for PyCon this year. I did a lightning talk explaining why (I start at about 8:00 minutes in).
One of the things I didn't expect when I released Cog was that people would take the concept and port it to other languages. There are implementations for PHP, Ruby, and Perl. And now, Doug Harriman has written another, so you can Cog in Matlab. I don't know anything about Matlab, I didn't realize this was even a sensible idea, but now it's real.
When I look at Cog now, I see things I'd like to change about it. Maybe there will be a more modern implementation some day. But it does its job well now. If you have text files that you want to do a little bit of processing on, look into Cog, people seem to like it.