ubun2

I am using VLC media player for ubuntu / linux and it is pretty good. It has played all of the videos i tried without any problems.
You could install this in a couple of ways
Through synaptic package manager
 

1. System->Administration->Synaptic Package Manager
2. Search for vlc and choose install

Through terminal window

1. sudo apt-get update
2. sudo apt-get install vlc vlc-plugin-esd mozilla-plugin-vlc

Please make sure multiverse mirror is present in /etc/apt/sources.lst