Mine is "Windtalkers", the 2002 movie starring Nicholas Cage. It was especially disapppointing to me, given the subject matter. The story of the Navajo codetalkers and the role they played in WWII had the potential to be interesting material. But John Woo, the director, instead made an absolute mess of an action film, with plenty of slow motion shots of Nicholas Cage grimacing like he'd just taken cyanide. Cage was terrible, but I blame Woo for not having any idea how to make the movie. I've never walked out on a movie, but I came close on this one.