Mpv, A Free And Open-source General-purpose Video Player.

Mpv is a fork of mplayer2 (see former post ) and effectively its successor. Mpv stands for mpv plays videos. Notable changes from mplayer2 include removal of lots of unneeded code, better OSD ( On screen display ) rendering (using libass), support for playing URLs of popular streaming sites directly ( link ).
It supports a wide variety of video file formats, audio and video codecs, and subtitle types.

There are instructions to build mpv, but being lazy I googled for a deb-package....
Go to http://ppa.launchpad.net/cellstorm/test/ubuntu/pool/main/m/mpv/ and download the package for your architecture.

I use gdebi to install it. Search for gdebi in Software Center.
Then right click the mpv package and choose Open With Gdebi Package Installer.

You can start mpv from a terminal :

Or in Files navigate to a video, right click and choose Open With > mpv Media Player.

For a full list of options type man mpv in a terminal.

The On Screen Controller (short: OSC) is a minimal GUI integrated with mpv to offer basic mouse-controllability.

User-local settings are stored in ~/.mpv/config. The complete list of options is located here. An example.
My settings :
hwdec=vdpau
vo=vdpau

You can speed up the player using the GPU VDPAU API. See here and here.

My card supports VDPAU ( Nvidia GT 330 ) partially : Feature Set A.

mplayer -vc help | grep vdpau in a terminal gives :  

ffmpeg12vdpau ffmpeg    working   FFmpeg MPEG-1/2 (VDPAU)  [mpegvideo_vdpau]
ffwmv3vdpau ffmpeg    problems  FFmpeg WMV3/WMV9 (VDPAU)  [wmv3_vdpau]
ffvc1vdpau  ffmpeg    problems  FFmpeg WVC1 (VDPAU)  [vc1_vdpau]
ffh264vdpau ffmpeg    working   FFmpeg H.264 (VDPAU)  [h264_vdpau]
ffodivxvdpau ffmpeg    working   FFmpeg MPEG-4,DIVX-4/5 (VDPAU)  [mpeg4_vdpau]

Playing a mp3 :