If you want to play video or music files and not worry about format, VLC Media Player is the best application for the job. With so many media formats out there, VLC Media Player is a catch-all player that can handle anything.
If you're looking for a great alternative to Windows Media Player, iTunes, RealPlayer and others, VLC Media Player is the application you need.
Now in its 1.0 release, VLC Media Player is simply the most stable, flexible and lightweight audio and video players around today. While other media players will play unusual formats after downloading a codec, or simply refuse to play things, VLC Media Player will not complain. In addition to this, you can also use it to preview files you are downloading, because it will play parts of files. It takes no time to start up either, so opening it up to preview something is no trouble at all.
VLC Media Player has great hotkey support, if you take the time to learn the shortcuts so it can be controlled without touching your mouse. If you're watching DVDs or video files through it, this is not an issue. For music, it plays more or less any file and features an equalizer and playlist creation. VLC Media Player isn't as intuitive asiTunes as a media manager, but it's a much more flexible player in terms of file formats. You can even use VLC to convert your files, and on top of all the formats and physical media it will play, many streaming protocols and TV capture cards are supported.
VLC Media Player makes it easy to add subtitles to your video files too - just add the SRT file to the folder where your video is kept, and it will automatically play with subtitles. The interface is functional, but by no means attractive - but you can download skins to completely change VLC Media Player's appearance. The preferences menu is comprehensive without being overwhelming, and there is extensive documentation online.
For video, VLC Media Player is the best application you will find. It's minimal interface is great for viewing, it's got excellent tools for effects, and doing things like adding subtitles is easy.