well i was going to say iTunes which actually uses Mac OS X's QuickTime layer to play audio. but theres also VLC
(looks like iTunes but allows plug-ins). i dont think theres a full version of Winamp for Mac yet but Googling for "winamp + mac os x" bring up a few results.
im assuming you dont like iTunes becuase you are used to its slow, annoying Windows cousin, or you dont like how it lists songs of the same artist or you just dont like how Apple forces you to use iTunes to sync an iPod.
i cant help you with the last one but you could try giving iTunes a try on Mac OS X as its fast and integrates with the system very well and you could try clicking the eye button on the bottom right to view genres, artists and albums without repeats for evey song.