Legendary for it's power, crypticly simple these are the things I've come to use and enjoy most abou the unix command line and standard binaries.

Stream digester which tokenizes or formats a stream of character data.

For me JavaScript is a wonderful language. From its roots in scheme it has closures and anonymous functions. Here are a few of the features that make javascript great to develop in.

Example of dynamically generating tweened animations with actionscript. Using a custom property to abstract the value away from the actions derived from it.

node.js is awesome!
The most exhilarating thing about it, is that using JavaScript for asynchronous callbacks on each event makes managing the context of non-blocking responses, wonderfully simple.