Quintessential Media Player is nice, skinnable, plays
anything - with the aid of a couple of free plugins, and most things without them - and as far as I can tell delivers clear, reliable sound quality no matter what else is going on*. Even though the non-dev release is about 4 years old, yeah. You can listen, make playlists, use effects, watch pretty colours, rip from CD, convert from any audio format to any other, autotag from CDDB, tag edit, filename edit, tag/filename edit en masse - and all with ease. . . etc.
* . . . which reminds me though - it could be say, the CPU or hard drive, being thrashed for whatever reason, when you're listening to stuff. Maybe not, just a thought.
Another one that's far more popular, and well, nearly as useful overall, is
Winamp. But QMP is as good as (or better than, IMO) the Pro version of Winamp (which costs), with available plugins for each taken into account.
VLC will also, apparently, do anything you want it to. I just don't like it much, personally. YMMV.
And there are others, but I can't remember them atm.