Cruel Intentions (1999)

Wealthy teens in New York have a lot of time on their hands.  Kathryn loves playing seductive games with her skintastically sexy step brother Sebastian (Ryan Phillippe) and anyone else she can lure into her web.  She bets Sebastian that he can’t bed Annette, a virgin who has made it quite clear she intends to wait until marriage to get down to business.  If Kathryn wins, she gets Sebastian’s prized Jaguar. If Sebastian wins, he gets to drive Kathryn.  Let the games begin.

There’s a lot of foreplay and implied sex here, but there are also some great views of Philippe’s backside.  His young, firm, smooth body is visible throughout, but it’s in a scene at the pool where his round tight bottom arrives after a nice dip.