It’s an open source media player for Linux.

It supports:
Physical media: CDs, DVDs, Video CDs
Container formats: 3GP, AVI, ASF, FLV, Matroska, MOV (QuickTime), MP4, NUT, Ogg, OGM, RealMedia
Video formats: Cinepak, DV, H.263, H.264/MPEG-4 AVC, HuffYUV, Indeo, MJPEG, MPEG-1, MPEG-2, MPEG-4 Part 2, RealVideo, Sorenson, Theora, WMV
Audio formats: AAC, AC3, ALAC, AMR, FLAC, Intel Music Coder, Monkey’s Audio, MP3, Musepack, RealAudio, Shorten, Speex, Vorbis, WMA
Subtitle formats: AQTitle, ASS/SSA, CC, JACOsub, MicroDVD, MPsub, OGM, PJS, RT, Sami, SRT, SubViewer, VOBsub, VPlayer
Mplayer can also save streamed contents into several output formats with the help of MEncoder.
From Ubuntu to download Mplayer:
Go to Applications → Add/Remove → Sound/Video → Search for Mplayer.
You may need to reload(download the latest packages available information before you’ll be able to find Mplayer).

After you’ve installed you can find more skins by searching it on google search.

Mplayer Screenshot