4. Britney Spears, "I'm a Slave 4 U"
"I think if you keep challenging yourself to do something different," Britney Spears told the UK's Observer in 2001, "people will see that and like that. But it's up to me to change." The video for "I'm A Slave 4 U" – the first single from that year's Britney, a laser-gun pop-funk track produced by then-on-the-rise duo The Neptunes – showed how far Spears was willing to go, at least in terms of potential dehydration. It's a sweaty romp in a dance club that looks fashioned out of a sauna, where Spears and her backup dancers fall under the spell of the song's skeletal beat.