MathJax and Stack Snippets
Two new technologies introduced this year have transformed the face of Code Review.
At the request of @VedranŠego, and with broad support from the CR community, we gathered enough evidence to convince Stack Exchange staff of the benefits of MathJax to the site. On April 7, MathJax was enabled!
In contrast to the hard work we had to do to earn MathJax, the Stack Snippets feature came as a bit of a present. In August, Stack Exchange developers informed us of the new feature that they had developed. It didn't take much argument to convince them that piloting a feature on a beta site was a good idea.
Rather than naming specific posts here that have made good use of MathJax and Stack Snippets, I have proposed them as categories for Best of Code Review 2014, so that we can all participate in picking out the best posts.