The Last Airbender. That movie can go die. It does not exist in the Avatar fandom. In fact, pretty much every M. Night movie. I haven't seen the Sixth Sense so I can't say anything about that. But The Last Airbender was just no.
Speaking of Avatar, Avatar. I despise that movie. I mean, technologically, and visually, it was stunning. But that was it. I was just watching a pretty moving art show and I love that Wayne Douglas Barlowe was on board for art direction. But in terms of story, it was ridiculous and predictable and very much the epitome of modern Hollywood, which I hate. Also, James Cameron is an ass. He did not have to buy the rights to the word "Avatar." Ugh.
All the Twilight movies.
Someone put Wall•E. You can still redeem yourself if you like The Incredibles. Hehehe

But number one worst movie was The Last Airbender. Also Eragon. That movie can go die too. Along with the books.
I actually punched a bloke in the face once for saying Avatar was better than Aliens........