The Amazon Molly is perhaps the most interesting. It exists as an all female species that is a sexual parasite on the two species that it arose from. It uses their sperm to stimulate its eggs but destroys and doesn’t use their genetic material and instead proceeds with a form of parthenogenesis https://en.m.wikipedia.org/wiki/Amazon_molly#:~:text=The%20Amazon%20molly%20(Poecilia%20formosa,essentially%20all%20individuals%20are%20females.