Are male, female, transgender and intersexed is too many sexes for you? Good thing you're not a Tetrahymena thermophila.
It has not two but seven sexes, and each one can mate with any of the others, which opens up the field considerably. Unfortunately, they all look alike.
Its sex is controlled by a gene called mat, but it is not as simple as one version of the gene encoding one sex. Instead, each allele of the gene sets out a series of probabilities.
There are at least 14 of these alleles, each offering a different set of probabilities.