I haven't seen the Usual Suspects, so I can't judge that one (it is odd that you seem to be assuming that we are going to give one particular answer, instead of thinking for ourselves).
I think ithe best was the one in The Sixth Sense. I saw the film without knowing that there was going to be a twist, and without having heard anything about it. Since I saw the film, I have read about many people having their experience of the film being ruined by idiots blurting out the twist before they have had a chance to see the film.