Ok I know that there will be many arguements about this topic but I feel very strongly about this lol. The saddest anime of all time is Air. I just finished watching it like a week ago and I still get sad thinking about it. I love watching it over and over again, it makes me sad but the characters are so lovable I cant stand it. It ticks me off LOL. I have the movie in my Qued in netflix and should be here tomorrow and I cant wait to watch it. But yes AIR is definetly BY FAR the sadest anime you will ever find. Im sure if you watch it you will agree.