I def agree on the Dobby thing. Though they made the 5th movie when the 7th book hadn't been released so that's alright, but they should have still put him in the 6th one at some point so the audience could remember him for the 7th movie. A picture or name mention would do.

And Snape revealing the half-blood prince was done retardedly since the whole movie never once showed Harry trying to find out who it was. Just 5 min of trying to find out who it was would have made a difference imo at the end of who was the prince.