Winter Bash is back on participating Stack Exchange sites in full effect, from 14 December 2015 until 3 January 2016.
Winter Bash is an annual event that can run on any Stack Exchange site that chooses to participate. Users earn “hats” for their gravatars by completing certain tasks (analogous to badges). Certain actions trigger the user receiving a hat, which their gravatar can "wear":
Sites vote explicitly to participate, and if the idea is welcomed by site's users, it will be enabled in the aforementioned period. It's important to know that even if Winter Bash is enabled, users can explicitly opt out if they want to (there will be "I hate hats" option on their profile page which will revert the site to its familiar look for the user).
So, it's time to decide if we want hats on our site. Vote on the answers below!