Free Media/Video Players

KMPlayer, Choosing a multimedia player used to be a real no-brainer. However, during recent times the raft of new features and updates added to classic media players like Winamp, Windows Media Player, and even iTunes have left the apps increasingly bloated. For those looking for a fresh alternative to these ballooning apps, KMPlayer could be your ticket.
KMPlayer has a small desktop footprint and its minimalist interface makes video playback quick and hassle-free. The player's interface is fully skinable, and there are some nice aesthetic touches, such as the changing of colour on the player with every new track.
There are all sorts of options to help you pimp and customize KMPlayer, such as visualizations, plug-ins and playback options. But the beauty of KMPlayer is that these are turned on at your request rather than being forced upon you at the outset.
KMPlayer handles both audio and video, and supports a wide range of different formats, meaning that once installed, you should never need to touch another player. Video playback is particularly impressive thanks to the range of processing tools available that allow you to sharpen, change picture properties, apply filters and even make video captures from within the program.
If you're looking for a customizable, light yet powerful video player, KMPlayer is exactly what you need.

I use this, it includes all the codec and has many skins, i found it reliable and easy to use

VLC is a powerful media player, playing most of the media codecs and video formats out there.
The media player that fills all your needs. It can handle DVDs, (S)VCDs, Audio CDs, web streams, TV cards and much more.
You don't need to keep track of a dozen codec packs you need to have installed. VLC has all codecs built-in. It comes with support for nearly all codec there is.
And what is more it can even play back the file or media if it is damaged! Missing or broken pieces are no stop to VLC, it plays all the video and audio information that's still intact.

GOM Player includes many codecs (XviD, DivX, FLV1, AC3, OGG, MP4, H263 and more) so you won't need to install separate codecs for most videos. For those videos that require a separate codec, GOM Player will find one and direct you to a place where you can download an open source version of the codec. That way, you won't get stuck with unnecessary codecs on your system.
AVI files can't be played if the index is broken, or if the file isn't completely downloaded. This is because the index is located at the end of the file. GOM Player's patented technology enables users to view files with broken indexes or that are still being downloaded.
GOM Player supports SMI, SRT, RT, SUB(with IDX) files for subtitle. You can specify margin, location, size, resolution, font and others. You can also enable shadow, view ASF files with subtitle, karaoke subtitle mode. You can even synchronize subtitle and video if there's any mismatch.
Along with different media format such as AVI, MPG, MPEG and DAT, GOM Player also supports streaming Windows media format (WMV, ASF, ASX). You can also watch DVD-quality videos with 5.1 channel audio output.

This may need extra codec for some media types

Kantaris is a new media player based on code from Videolan client (VLC) and Bass audio library. Kantaris has a graphical user interface similar to that of Windows Media Player.
Version 0.6.6 works with Windows 2000, XP, Vista and Windows 7.
The latest version of Kantaris has a unique new feature which to my knowledge no other player has, it can detect character encoding of subtitles by analyzing the text. This means that you never have to manually set the character encoding again. The feature is mainly for languages with “funny” characters, like Chinese.
Windows 7 has finally been released which you probably already know unless you have been sleeping under a rock. Since previous versions of Kantaris had some video quality issues on Windows 7 I needed to get a new version out fast. Hopefully the issues are fixed now, I haven’t tested it myself because I’m still running Vista but users have told me it’s now working fine. Another thing that has changed is that I’ve removed the Last.FM radio feature and the replaced it with music from Playlist.com (yes, I know the tab still says Last.FM). The reason is that Last.FM has decided that only paying subscribers will be allowed to listen to the radio from anything other than the embedded player at the official website. I don’t agree with this decision as I think that Last.fm’s open access to the API was one of it’s best feature and it made the service unique but I guess they not making enough money. Anyway I decided to replace it with searchable playlists from Playlist.com.