I should probably have started with this, but here's the list of built-in badges which are active by default:
First Reply By Email
Crazy in Love
Out of Love
I'm happy to give you the complete description of anything you'd like. Also, this is the badge creation screen, to give you a sense for what options we have:
Badge types are Gold, Silver, and Bronze, and Groups are Getting Started, Community, Posting, Trust Level, and Other.