I tend to use the term Jesus Freak or God nut to refer to religious fanatics of a Christian persuasion. I think it's notable that mainstream society in the United States doesn't generally treat fanatical Christians the way that, say, fanatical Muslims or fanatical Hindus or fanatical Jews are treated. It seems for Christians there's no such thing as too much, but with non-Christian faiths there are definite lines to be drawn. There's a lot of things that fundamentalists and other Christians do that when taken from a cultural viewpoint other than our own are just downright strange

I think a little cultural relativism when looking at religion is a good thing, even if you're religious yourself.