mytube.. most beautifully designed youtube client for windows phone..

Features:

  - Watch video while reading comments and browsing, and even listen to  it while using other apps
  - HD video support
  - Rate, comment and share videos
  - Browse playlists, and add videos to your own
  - Browse and subscribe to your favorite channels
  - Save videos for watching when you have a limited connection
  - Pin channels' uploads, favorites and playlists to your start screen
  - Double wide live tile
  - Offline playlists


Find it here!!
http://www.windowsphone.com/en-us/store/app/mytube/d994dce8-38f9-4ed3-ae6c-e334d4bd558c