It conveys both surprise and irritation, as well as fox hunts.
B: By Golly! Let us take him to the castle to give him food and shelter!
It is a sort of wink but more of an angry/annoyed wink; not a flirtatious wink. It can be kind of a way of making the other person feel like an idiot when they don't know what they're talking about or state something obvious or even false. The user can be implying they know something the other person(s) does not.
B: "Naw. -.O" <-Sarcasm
A: "Omgigawd! I'm so cool. :]"
B: "-.O Mhm, sure you are."