One of your sexes, perhaps: there isn't a single marker for sex (and some of those we like to think of such markers aren't binary, but we can drop those for this exercise)
Less trivial: https://en.wikipedia.org/wiki/46,XX/46,XY
https://academic.oup.com/bjs/article-abstract/69/5/279/61857... "Ovulation in a cytogenetically proved phenotypically male fertile hermaphrodite"
Ovotesticular syndrome: https://rarediseases.org/rare-diseases/ovotesticular-disorde...
> Histology of his removed ovary suggested that ovulation had, at some time, occurred. He had also fathered a child and this is believed to be the first case of a cytogenetically proved true hermaphrodite who is fertile as a male.
That's a single human body that produced both forms of gamete.
So, which is this individual, who produces both forms of gametes?
Am I, with no gametes, a null?