Agender (3.5e Trait)
From D&D Wiki
You have no gender.
Prerequisite: You must be part of a race with actual (separate) genders.
Benefit: You are not affected by harmful effects designated to a specific gender.
Drawback: You do not count as either gender for prerequisites and positive effects (such as meeting the prerequisites of a male-only prestige class). Also, you always suffer a penalty on checks to disguise as someone of a specific gender.
Special: You cannot have the Hermaphroditic trait.
Roleplaying Ideas: You may need to hide your lack of gender from others. Individuals of atypical "gender" are revered in some cultures; however, in others, they are killed at birth.