A lot of less technical music geeks prefer winamp, but as a more technical user I really love Foobar2000. doesn't have any of the flashy UI of other player, but the UX is really top notch once you learn your way around it. My favorite part is how it adheres to the pythonic principle of "Explicit is better then implicit" in playback. You have your library and your playlist, and you play things my adding them to your playlist from your library. Dead simple, and easy to do plenty of complicated stuff with. Also it has a huge plugin community, and can even cater to every audiophile whim, if you swing that way.