To use a wonderful quote from the Mythbusters:
"I reject your reality, and substitute my own"
I read a definition of an agnostic a few years ago that said something very much like "One who believes that whether God exists, or does not exist, that knowledge will be forever unknown or unproved by mankind"
In terms of the Big Bang - I tend to lean towards it, but to be honest I think I'm kind of "agnostic" about it, if you take my meaning.
(Angry Agnostic bumper sticker: I DON"T KNOW - AND NEITHER DO YOU!!)