The graph above represents the gender differences in emoticon usage among teenagers, taken from the book: Discourse 2.0: Language and New Media
Teenage girls use more emoticons in general, and in particular, the open-mouthed smile. The only emoticons males utilized more often were the winking face, associated with sarcasm and flirtation, and the sad and sleepy faces, associated with, well, sadness and sleepiness.
(h/t All Things Linguistics)
