I have played with many different media players on my Windows Mobile device and so far the best I have come across is CorePlayer.

If you have a HTC Kaiser then you are most likely aware of the display drivers performance issues(If not click here).  CorePlayer has a special option to help target this problem and increase the performance and it really does help!

The lastest version of CorePlayer comes with an in-built YouTube browser that is really effective and easy to use.

Click Here to download or view CorePlayer