We all know the basic smiley faces :-) and (^_^). I’ve picked up some other emoticons that seem more specific to gamer culture.

o/

Hello! A little man waving an arm. Used for greetings; one reply is \o.

\o/

Hooray! A little man cheering with both arms raised. An alternate to “w00t!”.

qq or QQ

Crying. Two eyes with tears streaming down. Usually used ironically, particularly in the phrase “less QQ and more pew pew”. Ie: stop whining and play.

O.o

Oh really? A face with one eye cocked in astonishment or scrutiny. Often used in response to inappropriate jokes and Quentin Crisp hats. Useful emoticon; I can’t think of a good alternative picture or phrase. Bay suggests O RLY?, which is close, but O.o doesn’t really connote skepticism.

Most of these I got from chatting in Eve Online, where most players are European. The O.o form feels particularly English to me. I see a fair number of these in World of Warcraft as well.