"He Can Only Hold Her" (Amy Winehouse)

Amy Winehouse was a tortured, talented soul whose star burned out much too soon.  Years from now, I have a feeling that her second album, Back to Black (2006), will be widely regarded one of the best pop albums of the 2000s—and not just because the decade was otherwise filled with Auto-Tune garbage; the disc stands on its own merits.  Salaam Remi and Mark Ronson's 60s throwback production gave the songs an air of familiarity, but then Winehouse flipped the tunes on their heads by giving them witty, irreverent lyrics that set them squarely in the 21st century.

If I had to choose a signature song for her, it wouldn't be the cheeky Ray Charles-indebted "Rehab," or the heart-wrenching addiction tale (disguised as torch song) "Back to Black."  I would choose the lesser known album closer, "He Can Only Hold Her."
To the casual listener, the vintage Stax-flavored track (which features members of the Dap-Kings, replaying portions of the obscure soul nugget "(My Girl) She's A Fox" (1966) by The Icemen*) might seem to be about Winehouse feeling torn between two men: she's pining for an old flame, and neither she nor her current boyfriend really know how to quell those feelings.  However, if you put the song in the larger context of the album and look at the narrative arc (she starts out by refusing rehab and then, along the way, confesses that she always falls back on bad habits whenever she gets her heart broken), it becomes clear that this song is about addiction.
Unlike every other song on the album, she sings "He Can Only Hold Her" in third person.  Curiously, she's able to acknowledge for the first time on the album that she's not merely a victim of circumstance but an active participant.  As an objective observer of her own situation, she finally realizes that clever quips, sex, and/or her old Donny Hathaway records aren't going to save her.  But the truly heartbreaking thing is, she doesn't know how to save herself.  
At the risk of sounding completely morbid, she wrote her own obituary.
The day she passed away in 2011, I listened to this track over 100 times, disappointed that she had become yet another entertainer to die before age 30.  As a fan, I'd sincerely hoped that, by recognizing her demons, she could exorcise them.  But that simply wasn't the case in the end.  Still, she left behind a solid (albeit brief) legacy of pithy, soulful music that will surely endure.

(*If you take a listen to the linked track, you might recognize the guitar playing of the late Jimi Hendrix.  The single was recorded about a year before Are You Experienced? would drop.)

"Valerie" (Mark Ronson feat. Amy Winehouse)

In 2007, NYC-based British producer Mark Ronson released Version, a collection of R&B/soul covers of alt/indie rock and pop songs.  As you can imagine, covering the likes of The Smiths, Radiohead, and Britney Spears on the same disc with Motown-style arrangements produced mixed results.  
But a standout track on the album was a cover of The Zutons' 2006 indie rock song "Valerie," featuring the late Amy Winehouse on vocal.  In fact, it's one of those charmed instances where the artist covering the song owns it so completely that you almost don't associate it with the original.
The collaboration came about because Ronson had co-produced Winehouse's 2006 hit album, Back to Black, which itself had a 1960s throwback feel.  Ronson requested that Winehouse choose a modern rock song that she could cover for the Version project, and she suggested The Zutons' song--a track that Ronson initially wasn't sure was a good fit for her voice and style.  
Ultimately, "Valerie" would become one of her signature songs.
And the reason is crystal clear: Winehouse's interpretation and immaculate delivery retains the humor of the original, only it's tinged with her ever-present, Billie Holiday-like melancholy, which pushes the soul quotient to the max.
(Plus, there's the added bonus of lighthearted studio chatter at the beginning of the track, where Winehouse references a bit of Dave Chapelle.)