Depending on if there are caps, or where they are/how arranged, here we go on text exotes:
1.)
o.o : blank stare, as in "You've just lost me" Or "I care about this...Why, again?"
2.)
O.o ; o.O : Confusion, usually used together.
3.)
O.O : Suprise, shock.

A trick played on a fellow athlete where the open hand smacks the target's testicles with the knuckles in a sharp, wrist flicking motion.

An anime style smiley used to express shock, or

shock, puzzlement, misunderstanding; raised eyebrow, skepticism

generally used in online chatting

A surprised, disturbed or confused emoticon.

it depends. either you use: o.o, O.O, O.o, or o.O there's a good chance it's for something you couldn't believe you just heard.

–emoticon

1. A commonly emoticon used on the internet to indicate confusion
2. A surprised look
3. (used to specify the feeling where you don't know what's going on)
4. Over-used in instant conversations like the internet short form of laugh out loud; "lol".

This emoticon has been used in several different ways. Some of them, you may recognize:

o.o , o.O , O.o , o_o , o_O , O_o , 0.o , o.0 , o_0 , 0_o , 0.0 , O_O , 0_0 , O.O

Aside from the ones given above, there have been several people who customized them. For example; o_______o , o_o;; , o_o" and so forth...