Gah, I cry so easily at TV Shows.
Number 1 would be Toshiko dying on Torchwood. It was too emotional
She was my favourite character and they really built up this huge backstory for her....and it won't be needed any more.
Number 2 would be Skins. Not Chris dying or anything, just Jal's big speech at his funeral, and her emotionalness (it's a word now) was like overwhelming.