Until recently, my favorite typeface was Bitstream Charter. Now, it's Source Serif.
It's not exactly sans, not exactly serif, which is what draws me to it.
It's the typeface that you see in a great printed book.
Because it's almost like Charter's next evolution, I can finally replace my once favorite typeface. As a bonus, it pairs well with the sans and monospaced Source Sans 3 and Source Code Pro.