I was checking out www.moviemistakes.com and I found those on top 30!
Nr. 10, American Pie, In the bedroom scene the girl is holding a clear cup full of beer. The camera goes off her and when it comes back she is holding a blue cup. The camera goes back off her then on her and the cup is clear again.
Nr. 19, Mr. and Mrs. Smith, The movie is supposed to take place in and around New York City, however during the car chase where Angelina and Brad are fighting off the three BMW’s, a wide shot clearly shows a street sign announcing Los Angeles.
But the movie with most mistakes is Apocalypse Now whit 396 mistakes! And actually two Harry Potter movies has the 3rd and 4th place. Harry Potter and the Prisoner of Azkaban is the 3rd with 287 mistakes and Harry Potter and the Chamber of Secrets is just behind with 284 faults.
Rupert Grind, Emma Watson and Daniel Radcliffe