Dragonesses, Gryphons, A giant elemental bird (but not her being actually made of the element but instead able to control it. Like controlling fire withoyt herself turning into KFC, or storms without being a damn lightning rod), Most of the mechanical creatures from Horizon Zero Dawn (Especially the Sawtooth/Ravager, Thunderbeak, and Stalker). Giant snakes (Milotic and Serperior from pokemon, for example), Dire Wolfess, Varkids from Borderlands (Basically giant bugs). Speaking of Borderlands, I'd fuck a Skag and Kraggon. But Kraggons are made of rock so I doubt sticking my cock in would work...
Also a couple cosmic horror cuties
I fantasize about becoming the priest of an eldritch horror cutie and slowly having my body and soul become one with her as some sort of cosmic "marriage". Truly being one hehe