Koreans, like most East Asians, use very different emoticons from the ones Americans use. In the US, we're familiar with the horizontal emoticons:
With these emoticons, emotion is expressed mostly with the mouth, though there are a few exceptions, like >:-).
Korean emoticons are vertical:
^_^" nervous (that's a sweat drop)
Also, as you may have noticed, the mouth doesn't really change--instead, emotion is expressed with the eyes or with other features.
Now, none of this is really news to the East Asiaphiles of the world. However, just the other day, I saw a really interesting usage that set my amateur linguist brain aflame. At the end of a very happy/thankful e-mail, an acquaintance wrote:
Upon further inquiry I learned that, in some circles, the length of the mouth can be used to indicate the strength of the emotion being conveyed (not, mind you, the fatness of the face conveying it). I guess the idea is that, the more characters you type, the more time/effort you spend? Any thoughts, intarwebs? (By which I probably mean Leslie.)