I'd agree with Jamie Lee Curtis' bathroom scene in trading places. That was pretty gratuitous. Also the scene where the (latina?) woman sits up naked in Eddie Murphy's new bed and announces, 'I was waiting for you!'
Katie Holmes in that movie about the psychic ... which one was that? In the psychic's vision Katie is standing by a car at night, opening her blouse. Good stuff.
Revenge of the Ninja: near the beginning a couple get it on in a hot tub while the evil ninja slides a poisoned dart into his blowgun.
I've always been a fan of the full frontal nudity in the old Tom Hanks movie Bachelor Party, where the girl who has always wanted him greets him naked in the hotel room.
And of course, perhaps the best gratuitous breast scene of all scifi/horror movies, French actress Mathilda May (yum yum) as a naked alien vampire in Lifeforce. After being recovered from an alien spaceprobe in the tail of Halley's Comet, she is lying on a hospital table on Earth. An entranced guard moves to her covered body, and abruptly her eyes open and she sits up, the sheet dropping away to reveal her perfect naked body. That was a great scene. Pretty cool movie, too!