Super Mario Amp 2
This is one of the few (but certainly not only) "side-scrolling" winamp skins; The windows look the best when tiled from left-to-right, MAIN, EQ, PLAYLIST. After that, the remaining windows will work in any order. Or you can put the first three on top, and the other three below them. Or you can stack them however you want, it still works.
Special thanks to The Shyguy Kingdom: http://tsgk.captainn.net/index.html
And to all the fellows and ladies who helped out at the WA2-skin forums.