Being old and somewhat set in my ways I use Winamp which has been my mainstay for many years.I have treated it to a rather nice translucent skin though.
I stand alone in my support for Xion, I see. I like it for its no nonsense plays audio files only attitude. Nice and lightweight. Reminds me of WA 2.9x.
My favourite is VLC Media Player. There isn't pretty much anything that it can't play. I also like its minimalistic UI. But, Windows Media Player has improved a lot. Very good player. With these two, I doubt there will be anything that won't be played. No complaints with these two.
I now use Windows Media Player Classic Home Cinema, I just started useing it I like it so far;VLC;WinAmp;Spider player;AIMP2 .
WMP 12 and if I rarely want some extra features, I temporarily install KMPlayer and then uninstall it. Till now, WMP 12 and K-Lite Mega Codec Pack have served me good.
I tried WinAmp and 1by1 and didn't like either. WinAmp left a lot behnd after uninstall, context menu options. AIMP2, MediaMonkey and WMP are about my top three right now.
The best windows player for 2010 is Media Player Classic Home Cinema. My second choice is Windows Media Player 12.