VLC media player is a great player who supports almost every video and audio codec. In video it supports mkv, flv, avi, mp4, wmv etc and audio codecs it supports mp3, mp2, aac etc. VLC player gives the personalization option to change skin of the player.
During movie play it gives subtitle option to understand every word. Audio streaming option let you select which language you used to listen. It play audio files directly which is packed in rar or zip extension. Very simple user interface, even a novice can understand.
Beyond All That it is totally free unless you want to Donate.