Every LOTR has sent me over the edge, when Boromir dies you can almost [i]feel[/i] the impact of every arrow pierce his (and your) heart, but he keeps on going to redeem himself for betraying Frodo. The music in that scene is simply tragic too. Toy Story 3, Up, and Snape's memory sequence in Deathly Hallows Part 2 were also just too much for me to emotionally handle. :P For tv shows, the departure of the Ponds in Doctor Who left me devastated.