Poll: HTML5 Turns 5! What Features Have You Used?

Happy Birthday HTML5!

Yes, I'd say that the 5-year anniversary of the blog post "Reinventing HTML" by Tim Berners-Lee counts as the birthday for the HTML5 working group and standard.  In 2006 the Berners-Lee proposed that a W3C working group be chartered for what would become HTML5.  He had some good insights on how standards have been adopted over time:

Some things are clearer with hindsight of several years. It is necessary to evolve HTML incrementally. The attempt to get the world to switch to XML, including quotes around attribute values and slashes in empty tags and namespaces all at once didn't work. The large HTML-generating public did not move, largely because the browsers didn't complain. Some large communities did shift and are enjoying the fruits of well-formed systems, but not all. It is important to maintain HTML incrementally, as well as continuing a transition to well-formed world, and developing more power in that world. -- Tim Berners-Lee

So in honor of HTML5's 5th birthday (how appropriate), we should all share which standards we've adopted.  Unfortunately I couldn't do a 'select all that apply' answer choice so just pick the answer choice that you use most frequently.  You can mention others that you've used in the comments.

What HTML5 Features and Other Emerging Web Standards Have You Used Most Frequently Production Sites?