Ask HN: What are some examples of good code?

I keep reading on HN that I'm order to become a better developer I need to write code everyday, and more importantly read other people's code.

What are some examples of good code that you've seen?

Personally I'm interested in Ruby on Rails and I've recently started going through GitLab-CE[1] but what is your favor code?

[1]: https://gitlab.com/gitlab-org/gitlab-ce