Tears<- I can imagine The Doctor saying "Her name was Donna, Donna Noble. She was the most brilliant, most clever and most important woman in all the creation, but above everthing, she was my best friend, my partner, my sister... then, I lost her..."
First and last lines of the female companions. I know many don't agree with me, but Donna's goodbye line, having no idea who the Doctor is, is the most heartbreaking.< Oh no! Totally the most heart breaking. We were all expecting/hoping for Rose's to be what it is. Martha, eh, seems plausible (and she did see him), The Ponds- well, their departure is a close second for me.