Turn-back Pony
A variant of the reverse cowgirl where the girl straddles the man facing away, sticks his dick in her ass and rides vigorously while looking back at her lover, moaning "I'm a pony! I'm a pony!" Ass-slapping is optional but recommended.
Hey Carlos, last night Brittainy did the turn-back pony and I'm still sore. I left hand sized bruises on her ass cheeks tho.