Deadbeef.

Why? It is simple. Fast and lightweight. As a matter of fact, it is also very simple to use. I loved foobar on Windows, i have "foobar" od linux - DeadBeef. I don't like AMP that are big as Amarok, i need something small, that won't interfere with my activities on desktop.

Decibel audio player. Low footprint, equalizer.

Audacious

50/50 with XMMS and SMPlayer, picked XMMS for the few mp3's I have. Don't listen to much music on computer except through YouTube.

I'm very fond of Clementine, and it got my vote the last two years, but it's lyrics feature seems to be inconsistent, and that matters to me.
Audacious doesn't intergrate near as nicely with kde as Clementine, but the interface is as easy to navigate as Clementines, and the lyrics plugin works better than Clementines.
Clementine may win me back another year, but this year Audacious gets the vote.

Audacious does the job I want, doesn't make coffee though.

Xmms though I give cmus and moc a lot of playing time in my shop also.
Xmms is for the bling.

moc and xmms

MPD with ncmpcpp or an iPad remote.
Has playlists, "random" mode and internet stream integration. I like the conky integration too.
Mind you, Pulse Audio does do its best to make MPD difficult to use but, then again, what doesn't Pulse Audio try to wreck...

MPD + ncmpcpp OR mpc. Lately I've been having a lot of fun with mpc. If you want to test your command-line-fu, give mpc a try with MPD!

I've put it on-line: http://tux.nl/Files/radio.pl

It uses $HOME/radio/radio.pref if available (I don't have a pref myself, as I change radio.pl to reflect my prefs)
radio.pref just is a list of .m3u files

In $HOME/radio/ you might place .m3u files
No manual (yet). Read the code if anything is not obvious.

Key bindings:

l or o - open a file-open dialog
a - switch to alternate station (the first two of the prefs)
0 .. 9 - index in playlist

Slim Devices squeezeplayer and squeezeserver are still pretty great, despite Logitech's determined efforts to strangle the golden goose.

Started using Clementine again after making this post. Wish i voted for Clementine again, i forgot how nice it is.
It's lyrics feature admittedly isn't as good as Audacious's, but if you change the settings so it only scans 'lyrics.wikia.com' and for 60000 ms, it seems to do the job even on slow internet connections.

Clementine is king.

Personally i hate AmaroK, i'd love to hear why users whom voted for it, enjoy it over the alternatives. (If you voted for AmaroK and have not tried any alternatives, don't respond.)

MOC
 

For just playing music, MOC rocks. Why do so many of the other apps on the list have to be so complicated?

MPD with Sonata, since I don't remember when, always reliable.