Labels, labels, labels.
I dislike "atheist" as a label because, a) it really doesn't tell you anything other than "I don't believe in God," b) makes god belief the default, which I think is a mistake, and c) the word comes with a lot of baggage.
But it's because of that baggage that I don't hesitate to tell people I'm an atheist. People need to realize that atheists aren't immoral, baby-eating pedophiles who want to kill and rape with impunity. They also should know that many atheists (most atheists that I know, actually) used to be sincere Christians. In fact, in my experience (all anecdotal, of course, though I'd be interested to see someone study this) often an effort to be a better Christian, studying apologetics and church history, biblical criticism and exegesis, leads people first out of fundamentalism and biblical literalism (which cannot withstand serious, honest scrutiny), and then out of belief all together.
I have come out as an atheist to friends and family (and, more anonymously, online), for much the same reasons that I came out as a lesbian. First, I dislike being dishonest, and I'm bad at it. My mom and I are very close, and I can't keep a secret for long. I couldn't play the game anymore; much like when I was playing at being straight, I knew all the right things to say and do, but it didn't take long before play-acting started making me sick. Also, as I said, I know that most people who hate atheists (and gay people, for that matter), do so because they don't know (or think they don't know) any. Just by being honest, I can open people's minds, a little.
But calling myself an atheist is starting to feel dishonest, too.
II don't believe in the Judeo-Christian God, for sure. There is an overwhelming amount of evidence to show that the claims in the Bible are flat wrong, from archeology and history to science to just basic logic (when two--or more--contradictory things are asserted as true, we know for sure that something is inaccurate). The God of the Bible is a logical impossibility. He's also, as written, a moral monster that I wouldn't worship even if there was proof that he existed. (Yes, I know, your God is love and Jesus died for you because he loved you this much, but I still get caught up in all the, you know, genocide and rape and slavery and misogyny, and have a hard time getting past that. I'm weird that way.)
But when it comes to belief in some sort of supernatural god? I'm agnostic. Now, I'm pretty sure there is no such being, and I think the world can be explained better with a naturalistic worldview, but if there was proof that such a supernatural being existed, I'd be an idiot not to change my mind about things. After all, reason and evidence is what dragged me out of Christianity, kicking and screaming. I don't think we can know for sure that there is no god, no supernatural entities, because, by definition, they would be outside our ability to test for. It's unfalsifiable. That doesn't make it true, by any stretch of the imagination, it just means that I can never say with certainty that there is no god, and I have to be willing to be convinced by good evidence. I do think it's highly unlikely, so for all intents and purposes, I live like an atheist. Therefore, I call myself an atheist.
It's sad that if I identified as agnostic, that label would come with a whole set of assumptions that irritate me. People, atheist and religious alike, see agnostics as wishy-washy, fence-sitters, intellectually lazy, cowardly, and believe we simply haven't taken the time (because we're lazy cowards, you know) to look at the evidence and come to a decision. And, of course, theists and atheists alike believe that if we just looked at the evidence, we would obviously come to their decision. That's just obnoxious. Maybe I'm weird, but I'd rather be considered a baby-eater than an intellectual coward.
And, like 'atheist', 'agnostic' doesn't tell you anything about my values. It doesn't tell you much about my belief system at all, beyond my lack of belief.
I'm a humanist. I claim that. Sometimes I modify that with a 'secular' preface. I strongly believe in humanist values, I live my life as a humanist, and I do think that the world would be a better place if everyone was a humanist (as if). Seriously, take a second to read The Humanist Manifesto. What could possibly be objectionable in that?
So I'm an agnostic atheist humanist. Or whatever. Labels annoy me, but, unfortunately, they seem to be necessary in this society. I try to avoid labels when possible, but I use what feels right in context when a label is needed. I've progressed a lot in the last couple years...from being 'Evangelical' to 'Spiritual' to 'Skeptical' to 'Atheist' and now I'm trying on 'Humanist'. I honestly can't say where I'll be next year.