My emotional threshold is rather low and so many films have a strong impact on me. Below are the main films that I can think of:
Titanic (of course)
Pretty Woman
The Curious Case of Benjamin Button
The Help
Avatar
I Am Sam
P.S. I Love You
Flipped (highly recommend)
Grave of the Fireflies
Marley & Me
Bridge to Terabithia
The Pianist
About a Boy
Edward Scissorhands
A.I. Artificial Intelligence
Watership Down
13 Going on 30
A Cinderella Story
On another note, my most favourite film ever is Notting Hill - I simply adore Julia Roberts.