The free multimedia player, SMPlayer, includes all the necessary codecs for you to play practically any video and audio format without having to install more external codecs packets: just install SMPlayer.
A feature that truly stands out in this player is that it remembers the options of all the files you play, in other words, if you start to see a movie but you have to leave, when you come back and open it it'll continue where you left off and with the same options you had activated: soundtrack, subtitles, volume...
SMPlayer Portable can also play just about all known video and audio formats, and it includes several interesting functions such as playing YouTube videos, or downloading subtitles directly from opensubtitles.org.
Other more advanced functions include: audio and video filters, changing play speeds, audio and subtitle synchronization, and video equalizer, among others.
SMPlayer's interface is fully customizable and includes several icon themes to easily change the player's look.