Ruby: anything written by _why (if you can find the source) He once gave a whole presentation on the splat operator and it's bizarre uses that gave me goosebumps. A true artist. The code twists and contorts ruby in unimaginable ways.
JS: anything written by TJ hollwaychuck (express, mocha, etc...) Express is so simple but powerful, when you read the source you can't help but wonder where the rest of the code is.
Python: anything written by Kenneth Reitz (Requests, legit, records...) This guy can lay down some serious Python and gets things done. He writes the batteries that python should have had included.