A winky face denotes playfulness.
It is used as a way to convey the playful sentiment in a medium, such as text, where emotions can't otherwise be displayed.
Depending on the context, it can be flirtatious, but usually denotes joking.
Jess: Chris asked me if I was free tonight Chloe: did he put any emoticons?
Jess: Yeh he put a winky face at the end of the sentence Chloe: HE WANT'S YOUR VAGINA!!
The face one makes when they want to have sex with someone. Mostly happens when drunk but can be when sober and just extremely horny. A face that says it all, no words are necessary....the face (especially the eyes) say "I want you to make love to me. NOW"