Today's Doctor Who's Day topic is saddest episode. I have a feeling the saddest episode I'll ever watch will be Amy and Rory's last episode, but since I won't get to see that until later this year, I'll pick an episode that's already aired.
I'd have to say that David Tennant's last special was the saddest episode of Doctor Who. It gets depressing as he visits all his former companions to say good bye, but then things get really sad. I lost it when Ten declared that he didn't want to go just before regenerating. Even though I knew Eleven was on the way, it was hard to watch my Doctor leave. Plus, it's pretty much a guarantee that if the Doctor cries, I will cry.
What do you think is the saddest Doctor Who episode?