Buzzfeed writes:

Before his untimely death, Heath Ledger began directing a video for Modest Mouse's “King Rat”. Unfortunately he died before the video was completed, and it has been languishing in limbo until now. Watch Ledger's music video, completed by his associates at the Masses, a violently unabashed commentary on illegal whale hunting.

Update: According to YouTube, "This video contains an audio track that has not been authorized by Sony Music Entertainment. The audio has been disabled." Full version here.