Hah, it's funny how much I've thought about this, and I usually thought I was alone in that. When posting messages on various online message boards, I most commonly use example #3, to allow the message board software to detect the ":)" without the final ")" interfering with the image transformation, as it sometimes does.

However, I hadn't really thought about the method #1 (discussed above) before. In the case where the emoticons are not converted into image-based smileys, this should truly be the answer. However, in a system in which they *are* changed into images, then you'd lose your closing parentheses, rendering the parentheses useless.