I have three for this category, all based on true stories with my rating of how many boxes of tissues you'll need:
The Miracle Worker - the Story of Helen Keller 1 Box
The Ghost of Flight 401 - 1 box (with tingles up your neck)
Who Will Love my Children - 2 boxes (with lumps in the throat)!
I have The Miracle Worker on DVD, but the other two aren't available as far as I know.