Foobar2000 - supports embedded cuesheets so each album is only a single file, not the seperate .cue that I have had to have in the past.
Good plugins, including loudspeaker equalizer which gives me the bass that I want, and vlevel which makes it usable at night time removing the difference between well mastered stuff and overcompressed modern crap mix jobs.
+1 For Foobar2000. With tweaking can do everything you could want from a winamp classic super simple player to a full-on organiser/tagger/syncer etc. etc. And its memory footrpint will always be lower than the competition. (Stay away from dodgy plugins though).