IF you can find it, try The Day They Gave Babies Away.
This film is so sad that scientists researching tears actually used it on their test subjects because it was guaranteed to make them, and anyone else within range, bawl their eyes out. I swear I'm not making this up.
Thanks for all your suggestions everyone. Ive seen a lot of them but there are few pretty good ideas here. Im almost reeady to lock myself in the house with some ben n Jerrys, a big bar of dairy milk and a mountain of kleenex