Recs.
Updated
VLC is a free and open source cross-platform multimedia player and framework that plays most multimedia files as well as DVDs, Audio CDs, VCDs, and various streaming protocols.
SpecsUpdate
Pros
Pro Out of the box support for almost any audio or video file format
VLC reads almost all music and video without codec installation. It has a wide range of supported encodings.
Pro Surprisingly Lightest on Resources
Yes. Lightest. Even better than the ones known to be light. Both when playing music, only a single song or when playing a video. Either in terms of Ram and Cpu. Compared with almost all, including the ones from Windows like mpc-hc .. or light ones from Linux like Alsa Player, Audacious, SmPlayer .
Cons
Con Lacks libraries and advanced music player features
VLC is a media player first and foremost. There is no library management, aside from playlists, usage of tags is very limited, no rating system and VLC is best at playing a file directly from a folder as opposed to helping you manage or find good songs in your music library.