Ask HN: Whats your “zen” software stack?

I'd love to know what sorts of software stacks "feel" right to people. Everyone has their own way of thinking, and in my experience when you find that particular method/language/framework of coding that works in a similar way that you think I've gotten this wonderful zen moment.

I'll start: For me as a web developer its recently been Node.js with a browserified frontend. Its easy to pick up a module/concept, write it as its own little machine, put it down and hook into it from the bigger structure. I can quickly zoom out to the larger view of the project and dig right back down to a problem area. I get to make a machine to handle a thing once and only once, and don't ever need to repeat myself.

What makes you giddy to work with?