This.
And also The Righteous Brothers’ Unchained Melody.
for sultry, “Love Letter” by Bonnie Raitt.
for naked vulnerable emotional passion, “Fumbling Towards Ecstasy” by Sarah McLachlan
… with honorable mention in that category to “Bat Out of Hell” by Meat Loaf
for OMFG how’d that get on the airwaves, “Bells for Her” by Tori Amos
“Brown Sugar” by D’Angelo from the album of the same name.
I actually find The Night kind of sinister. And not in a good way.
It’s primarily the music, but the lyrics, too.
Yes, there’s some sexy aspects to the description, but there’s also a lot to it that just feels like he’s being drawn to his inevitable doom, and he knows it… Which is SO not sexy…
Dogs of Lust - The The
I’m surprised no one has mentioned Closer by NIN.
Bad Touch - The Bloodhound Gang. Naughty chimps. 
On a more serious groovy note, Prince - Incense and Candles. It’s kind of hard to pick Prince songs for hot and sexy - too many to choose from!
Oh, for fuck’s sake. Prince now uses the dreaded Autotune, too? Fuck!
Both of these songs are way out of character for me, and far outside of my musical tastes, but I believe they are unbelievably sexy:
Umbrella by Rhianna
Don’t You by The Pussycat Dolls
They were probably engineered by fat old white men in suits to be as sexy as possible.
I’m an autotune hater, but I’ll say this for Prince’s use in this song - I hadn’t noticed it as detracting from the song, and he doesn’t have to use it (unlike a lot of modern singers) - I consider him one of the best pop vocalists alive. Autotune, like intense close-ups, shaky cam, and lens flares, is a technique that can be used to great effect as long as it’s used judiciously and sparingly, and Prince is not someone to back off of a fun new technique. 
Count me in on the NIN songs.
Other than “Closer”, I also like… “Big Man With a Gun”. Which I think is about rape. But I pretend it’s about S&M.
I also like Ludacris’s “What’s Your Fantasy.”
Can’t believe I didn’t mention: almost anything by Norah Jones. “Come Away With Me” is a good example. http://www.youtube.com/watch?v=lbjZPFBD6JU
Jason Mraz–I’m Yours. It makes me melt.
Here’s a couple of lesser known
Leonard Cohen-I’m Your Man
Morphine-All Wrong->Whisper
I’m going to go with
Madonna - Erotica
Ana Laan Paradise
The song could melt Pluto at aphelion.
Many good choices. I’ll add:
Miracles, Jefferson Starship off the Red Octopus album.