Different anime faces you may see: ^_^, >_>, <_<, v_v, -_-, ;-;, T~T, o_O, O_O, o_o, O_o, etc.
Brenda: Hi ^_^
Bob: How are you?
Brenda: Not good -_-
Bob: What's wrong?
Brenda: I have lice >_>
Bob: Oh GOD! STAY AWAY FROM ME!
Bob: YOU SICK FREAK!
Brenda: It's probably my anime faces... ;-;
O_O = shocked, omg, kinda thing other forms O_o O.o O.O o.o
._. = another form of O_O only a little stronger
-_- = annoyed, ugh, oh boy other forms -.- -_-; -_-'
-_-; O_o' ^-^' = extra things showed here are sweat marks meaning thing that shock and or embarras one.