1, an exclaimation made after a moment of incredible stupidity or massive failure.
2, a facial expression with crazy eyes and a stupid lip.
3, when accompanied by a " :3 " indicates happy moment, or blushing with out making the user feel as stupid as they would if they wrote *blush*
guy 1 "she's fiiiiiiine, think I'll get any tonight?"
guy 2 "she's a lesbian."