United 93, 2006
I knew from seeing the trailer for this film that it would be upsetting. In fact, I didn't see this at the cinema, but waited till I could watch it alone at home.
I made the right decision there, although I was surprised at how throughout the majority of the scenes on the plane, my strongest emotions were tension and fear. The passengers had heard what had happened at the Twin Towers and gradually realised it wasn't a "normal" hijacking.
So this gets a 3 tear rating from me. To know you're very likely to die in the next hour and make a phone call to those you love to say goodbye must be the hardest thing to do.
Even typing that last line has sent the tears running down my cheeks!