[b]note this is a list of all that I know of that works...[/url]
I have to side with graedus, Amarok rules ;-)
If you're used to iTunes or Winamp Amarok would be very easy to use (I personally find it a lot easier then iTunes). It's also included with PC-BSD
XMMS is very good if you like Winamp or other CD Deck on the Desktop style players. It's also light weight and I've used it often, very good program as long as you don't need to search their support forum <_<
Kaffeine is also quite nice, the current build has been quite stable compared to last year... If you liked Windows Media Players style of interface, Kaffeine is quite different but the user interface concepts are mostly the same. It's also included with PC-BSD and handles Video. - Kaffeine is probably a better choice if you like the graphic representation of sound playing.
MPlayer (KMPlayer for gui) is arguably the best Movie Player in the software world.. plays near darn every thing with the right codec. I find it not especially fun for Audio only but it makes a good browser plugin for my fav radio station
;-). It's also included in PC-BSD in command line and GUI versions, GMPlayer GUI (GTK+ rather then KDE libs) is in ports too.
VideoLANClient (VLC) is very good and works for both Audio and Video - very good software. I used to use it for DVD so it's stable enough I guess and it plays a lot of formats. I suggest installing from ports if you use it rather then any PBI, I think they tried to castrate it's format playing ability awhile ago.... The PBI Developer of it correct me if I'm wrong.
Totem, a Gnome Movie Player should also handle music fine, you might prefer this if you are used to using Gnome.
Rhythmbox, a Gnome music player originally inspired by iTunes. Unless you prefer Gnome/GTK+/GSTreamer I'd suggest using Amarok instead for the desktop integration. Other wise I guess this is Gnomes equivalent to Amarok hehe.
KPlayer, a GUI front end like KMPlayer that uses MPlayer as a back end, very good
but like MPlayer better suited to video
then audio files.
Xine is a movie player but can also handle audio, I have never actually used it 0.o. Kaffeine and Amarok (iirc) by default in PC-BSD are set up to use Xine lib's as part of it's playback engine. Xine is however not installed on PC-BSD.
Banshee is a C#/GTK+ music player that seems simuliar to iTunes/Amarok. Depends on mono...
JuK is a KDE Media Player, might be the standard or old standard issue actually. Never used it but you might like it if you like to organize your music a lot.
BMPx and BMP, never really used them but they should work fine. BMP is a fork of XMMS and BMPx is a replacement for BMP, it goes to a more WMP style interface.
Audacious and XMMS2, a fork of BMP and a player based on XMMS respectfully, no references..
I still suggest Amarok, easy to use, powerful, and can blend into both the player window (iTunes/wmp) and player dec (winamp/xmms) styles most people are used to.