A music player that fundamentally changes the way music is consumed and shared. It decouples the name of the song from the source it was shared from - and fulfills the request using all of your available sources. (Free)
A high-definition audio player for sophisticated music lovers. With support for all contemporary audio file formats and an elegant interface that focuses exclusively on music, it gives users the power and the freedom to organize, customize and savor their digital music collection at the highest possible fidelity in any circumstance. If you've invested in premium audio hardware, you should have the best audio software. (Premium)
A minimal, beautifully designed music player for the Mac. (Open source)
The standalone music player based upon your iTunes library. Fetch you Music, Movies, TV Shows and Podcasts.
The Google Music player for your Mac - Now with All Access support
More info on G-Ear Player.
Additional info regarding Google's New Play Music All Access Service:
Google Launches “Google Play Music All Access” On-Demand $9.99 A Month Subscription Service
The Advanced Music Player for Mac OS X.
Premium product ($19.95), however a 30 day free trial is available.