Then there's those of the Z type. The kind that doesn't fit labeling. Say, those born of a Great Old One.

but less nonsensically, "Don't wanna tell", "Male", "Female" and "Other" should cover most. If people want to specify further, the bio is a nice place to do so. It just won't work practically to cover every gender option possible. Not everyone will bother to add a gender, and of those that do, we suspect that the vast majority will use either male or female. At least if you go with normal gender distribution for a human population. 

and you can't exactly claim that the options not specifically male or female aren't covered by "other" can you?