:) is a smiley face, if you make your head cock to the left.
:( is a frowny face, if you make your head cock to the left.
:D is a big smile, if you cock your head to the left.
>_< is a discusted face.
-_- is a glare.
O_O is a wide-eyed face.
o_O is a confused face.
;) is a wink, if you cock your head to the left.
:O is a face with the mouth spread into an O, if you cock your head to the left.
..^-^
(o o)
(oo) Is a horsey! Look at the face! See, see?

XD is a big smile with eyes. One of my favorites, and HorseGirlMishi taught it to me!