If you're on a Windows machine, I highly suggest you use Media Player Classic if you're not using it already. You can download it with the K-Lite codec pack here:
http://filehippo.com/download_klite_codec_pack/

Plays almost everything. But one feature that is less talked about is how customizable the UI is. I have mine set as just the window plus the seek bar. Every other function that I would want is assigned to shortcut keys. It really does save a lot of space and eliminates any distractions while you're watching video in a window.