Contrary to popular belief, QQ is not a set of crying eyes. It actually originated with the advent of Warcraft II. On battlenet, you could press ALT+Q+Q to immediately exit the match and program. Thus the term "QQ" was to tell people to just quit because they are unskilled. The term later developed and lost it's origin and is usually mistaken as crying eyes.
In contemporary gamer culture, QQ has become the mainstream emoticon for crying eyes, though it is still often used in it's traditional sense.