Her tight ass

you spread her legs apart a little more, and tease her asshole with your dick, causing her to breathe heavily. "Stick it in..." she moans. 

Pulling back into position, you slowly slide your cock in, feeling her ass slowly grant you passage, gradually getting deeper, as she gasps in pleasure.

Within minutes, you're fucking her like an animal, thrusting wildly as she screams in delight, and cumming violently between her legs, as she passes out.