foobar2000, because I'm an audiophile. It can handle any audio codec, any codec profile, can provide spectrals of audio and bit sample rate as well as custom output control and mix management. Works with a COM automation server and CWB hooks. Fully integrated ripping and converting utility, playlist manager, and ID3 tagging standard support. Wholly customizable and skinnable with an extensive developing API. Oh, and it weighs in at around 7000kb as far as ram is concerned.
Winamp has nothing on that.