There is absolutely no other definition for an o face besides the face a youtube viewer makes when he or she is craving an outro performed by Tobuscus.
Also known as "outro-jingle face," or "outro face"
I was totally having my o face on, and then he finally fufilled my needs.
Tobuscus: You had that outro-jingle look on your face - no offence. That's a compliment. A very attractive feature in a lot of cultures, called outro face - look it up! - or o face, for short.