SMPlayer
SMPlayer uses the award-winning MPlayer as engine, so it's able to play the most known video & audio formats without any codecs.

SMPlayer uses the award-winning MPlayer as engine, so it's able to play the most known audio & video formats without any need of external codecs: avi, mkv, ogm, mpeg, vob, 3gp, asf, mov, wmv, mp3, ogg... You can also play DVD discs and Internet streams.

Special care have been taken with subtitles. It supports srt, sub, ssa, embedded subtitles in Matroska files, DVD subtitles...
SMPlayer subtitles can be very nice, you can choose font and size, and even colors for the subtitles.

One of the most interesting features of SMPlayer: it remembers the settings of all files you play. So you start to watch a movie but you have to leave... don't worry, when
you open that movie again it will resume at the same point you left it, and with the same settings: audio track, subtitles, volume...

Here are some key features of "SMPlayer":

Audio track switching. You can choose the audio track you want to listen. Works with avi and mkv. And of course with DVDs.
Seeking by mouse wheel. You can use your mouse wheel to go forward or backward in the video.
Video equalizer, allows you to adjust the brightness, contrast, hue, saturation and gamma of the video image.
Multiple speed playback. You can play at 2X, 4X... and even in slow motion.
Filters. Several filters are available: deinterlace, postprocessing, denoise... and even a karaoke filter (voice removal).
Audio and subtitles delay adjustment. Allows you to sync audio and subtitles.
Advanced options, such as selecting a demuxer or video & audio codecs.
Playlist. Allows you to enqueue several files to be played one after each other. Autorepeat and shuffle supported too.
Preferences dialog. You can easily configure every option of SMPlayer by using a nice preferences dialog.
Translations: SMPlayer is fully translated into Spanish and German.
It's multiplatform. Binaries available for Windows and Linux.
Free and opensource.