You'll probably think: oh no, yet another iTunes desktop player! It's true that the Mac nowhere short of this type of application, with each one more or less resembling the other. So what would make you go for X-Tunes.
For one, the interface is fairly sleek and discreet. It's unobtrusive and easy bring up thanks to a key combination. You can also tweak the opacity and fading delay. I also like the fact that it is only a preference pane item, so you have a proper menu from where you can adjust the setitngs. It's a shame that unlike many other iTunes desktop player, this one doesn't appear in your menu bar.
Although the player is fairly basic and will show only the typical play buttons, the fact that it's GPL means that adventurous programmers out there can play around with it and create something a little more original.
Still, X-Tunes remains an unobtrusive desktop player for iTunes with good keyboard controls.