I'll post two, one sexual fantasy that is within the realm of possibility, but isn't very likely. And the other is my imaginative fantasy, something that's outside the known realm of possibility.
My sexual fantasy is pretty simple really. The kind of guy that absolutely turns me on more than anything are the young and muscular sort of guys from sites like Corbin Fisher, or Sean Cody. In my fantasy, I'm the bottom in a very slow, passionate, and sensual gangbang with a large group of guys like that.
As far as my out there fantasy, I'm obsessed with vampires, demons, and other similar creatures. I was obsessed even as a little kid. Would love to meet a vampire, or a demon of sorts one night and not know it. Go home with said creature who's intentions are to kill me for sustenance, though somehow my meager mortal sexual prowess impresses this creature enough to make me into one as well.