Most guys are into threesomes I know, but for me, I find bisexual girl ffm threesomes to be extraordinarily hot. I find the idea of a girl enjoying the pleasures from both a man and another girl at the same time to be so damn hot. Because of this fetish, I've also gotten into girls licking another girls pussy full of the man's cum. To clarify though, my fantasy doesn't come from fucking lesbians or finding them hot, it has to be a bisexual girl.
My girlfriend is bisexual herself, and I wish she would indulge into my fantasies, but she's pretty vanilla.