People applauded in the LOTR, FOTR, when Aragorn chops off that Uruk-Hai's head. Y'know that big leader one, the really mean one. and they're on the banks of that river. I think it's when Boromir gets killed and Aragorn is trying to run down to him but that big guy stops him. or something.
Also, in Jurassic Park, the very first one (which was so amazing when it first came out). when the kids are in car and the T-Rex's eye appears at the window, a man up the back of the theatre yelled out "OH MY GOD!" it was so funny. but i also hid under my seat in that movie. Hey, i was just a kid!