Totem is the official movie player of the GNOME desktop environment based on xine-lib or GStreamer. It features a playlist, a full-screen mode, seek and volume controls, as well as keyboard navigation. It comes with added functionality such as: More info »
Actualy there are some problems... For example searchbar does not work with some flv videos and so on. But it is better and better with every release.
I am on Ubuntu and I use this all the time for my music and videos. It works great. it can play just about everything. I have never had a problem with it.