PJ's LoTR: Return of the King
It's aged really badly hasn't it. :(
From the glorious epic I saw in the cinema several years ago to watching it at home this weekend, my only thoughts were what went wrong. The effects looked awful, the dialogue seemed hammy and it was just not enjoyable any more. I can sit through Fellowship of the Ring several times, but it seemed that the further into the story he went, the more changes Peter Jackson just had to make.
After this, I fear for the Hobbit, if he is bought back in to make it.
And to top it off, following it I saw two episodes of Legend of the Seeker from Sam Raimi based on the Terry Goodkind books. They seemed a class act by comparison.