It's the Amy Winehouse clip that stands out from all the rest for me. I only fully realised why after reading Sasha Frere Jones in the New Yorker. Amy starts of unsteady, even unfamiliar with the song, and the backing singers are no better. She settles down quickly to a level of capable execution including seldom seen smiles punctuated with more familiar looks of incongruous zoned out distance.
Just before the two minute mark Amy steps-up and takes the song somewhere different than previous renditions. She pulls a devil sign of the horns at that moment but let's not read too much into that because as if to prove she has another two gears above every other singer on the planet, Amy ends the song with a voice that works the crowd like a machete in 90's Rwanda. Extraordinary. All in all, about sixty seconds of visibly trying and the audience are instantly won over.
I've no idea why she was so unhappy. I don't think it was just the drink and drugs. Sometimes drink and drugs are brilliant if a person is deeply unhappy. Then they start to contribute to the unhappiness and nobody can remember what started where.