I use winamp for mp3s, vlc and bsplayer for videos. Vlc is very expanded in what codecs it has. Maybe it's just that my laptop is juiced up, but I've also been able to play any region-coded dvds on it. ^^ It makes my life happy.
Microsoft Windows Media Player 11 because its 1.Microsoft 2.Good Looking Interface 3.Nice Library Organization 4.Matches Vista
I think iTunes is an awesome player. music online sound as good as the software produces it and iTunes does a splendid job.