@Henrik phil,
I personally call myself an Atheist on the grounds that I do not believe in God. For many years prior to utilizing this label, I had considered myself to be an agnostic, because I know there is not currently a way to enitrely prove or disprove the existence of a God; there may even never be a way, and therefore no-one can currently 'know' whether God exists or not. However, from the evidence I have looked at, I have decided that I do not believe in a God; it seems rather irrational to me a lot of the time. Therefore, I call myself an Atheist (when not using the label 'Bright' of course, please follow the link in my signature for more info). This is because I see knowledge and belief as two seperate things that people regularly combine, in both correct and incorrect ways. For example, some people say that they 'know' God exists, which is obviously not possible unless they've got an estranged definition of 'know'.
Without getting into a dispute about what it is to 'know' and what it is to 'believe', I did read somewhere that Agnosticism and Atheism could be combined on the grounds that to 'know' and to 'believe' are two different things. Obviously, it would be immensely irrational to say that you 'know' God exists but you 'believe' he doesn't. So really, if we are to say that agnosticism is a lack of knowledge for whether God exists or not, everyone should be an agnost, because surely no-one can 'know' whether God exists or not, but only 'believe'.
Anyhow, labels are genrally inaccurate as you can see from everything I've just mentioned, and, although my general beliefs haven't changed drastically, my label has, because I find it more efficient to use 'atheist' to make it clear that I do not believe in a God. However, this occaisionally makes it hard to explain to others that I am also totally aware that God
could exist, and that I can't entirely disprove that idea,just as others cannot prove it.
I hope that may have helped, or at least been slightly interesting.