I agree with Bill D. and Rapaire.

It's also fun, occasionally, just to play around with them, to see how expressive you can get with static letters.

(I think the animated ones are a dirty, intrusive, and nasty cheat)

They have Emoticons in Japan, too (based on manga faces), but those are right side up: ^_^ is "happy," ;_; is "tearful," o_O is "astonished," and ^_^' is "embarrassed." (that apostrophe is a little drop of sweat on the brow).