I like Media Player Classic the best...

At one stage quite a while ago I was having a lot of trouble playing a lot of downloaded video's... I downloaded a BRILLIANT K-Lite codec pack which came with Media Player Classic, and played absolutely everything... what more can you ask for..

Everyone had been recommending VLC as the best, but I only got it after coming across a video that wouldn't play on Media Player... It worked on VLC and I tried using VLC for a while, but it actually was a bit slower than Media Player. For larger video's though, sometimes they play smooth in VLC and not Media player, and sometimes the other way around.... So it's handy for a backup when i'm having trouble with Media Player...
But it's definetly the back up..

Media Player Classic all the way! :-)