Like WarKat said before me, I don't see too many characters that are agender / genderless. Even if they are, I never truly see it in tag form. It seems there are quite a lot of genders to choose from, most of which are not even heard of. I feel as though one of the reasons as to why someone's character is a male or female is because those are the most common genders and simple to understand. Genders such as androgynous, trans, cis, gender fluid, etc. can be a bit confusing at first to those who don't necessarily understand those terms. It would take a bit of research to apply those traits to your or someone else's character in order to gain a somewhat accurate and natural interaction ICly.
As for creations, I do have one character that is androgynous.