As a kid the only movie that I cried in was Transformers the Movie. That scene where Optimus dies was so sad and devastating. I tried to keep from letting my friends see me cry though, but it was so sad.
Grown up for some reason the opening of the Lion King made me tear up, I guess the song was that powerful. I know I was crying during the war opening war scenes in Saving Private Ryan, just seeing all those men being killed got to me. I know that any movies where animals get hurt or killed will automatically start me weeping. Oh and the one scene in Miracle on 34th Street that gets me every single time I see it is the scene in which Susan (natalie Wood) is watching Kris Kringle work and a lil girl is brought up to see Kris by her mom. She doesn't say anything because she can't speak english. The mom had just adopted her from a dutch orphanage, and explains that to Kris, and when Kris begins to speak Dutch that lil girl's eyes light up. Gets to me each and every time.
I'm sure there are more movies, but I can't think of them right now.
Oh and the Ewok scene hurts still, it's so sad.