There's a moment in Manhattan, with Ike and Tracey in bed, sitting watching a film on TV while eating a Chinese takeaway. Ike half-scorns Tracey for spilling some noodles on the sheets, then she says something cute, and, aware of his half-scorn, he kisses her shoulder and touches her. It's really nice.

Or that first kiss in Before Sunrise. Or the final scene in Before Sunset.

"Brotherly" love? Has to be the "one shot" scene between De Niro and Walken in The Deer Hunter. Ouch.

Sex scene: Laura and John in Don't Look Now. It's too serious to be erotic, too tragic to be stimulating, too real to be looked "down" upon.

There is a scene in A History of Violence which reminds me, but transcends, the one mentioned from Donnie Darko. Coincidentally, it also takes place on the stairs, between a husband and wife, after a rather stressful narrative arc; it verges on disturbingly violent, and Maria Bello ended up with real bruises on her arse as a result during filming.

Cronenberg understands the notions of sex as good as anybody, I think. Crash has some of the most extraordinary sex scenes I've ever seen, with deep psychological undertones.

Along similar lines, Lynch's Mulholland Dr. and Lost Highway's sex scenes, the former between Naomi Watts and Laura Harring, the latter a frightening, disturbing portrayal of masculine paranoia, a slow-motion sex scene between Patricia Arcquette and Bill Pullman.

For a challenging, complex and frank scene (one which merits an "Adults Only" sticker on the DVD case over here), check out Vincent Gallo's The Brown Bunny.