Ano Hana is the saddest and my favorite anime. That last scene I've rewatched so many time and cried my eyes out every single time.
So Manly ;)
I'd also say that the Ef - Tales of Series are also sad, but not that much of a tearjerker, but it does hit those feels.
5 Centimeters Per Second is a really sad movie about realistic childhood romance that you never see in any other anime.
First Three Episodes of Sunday Without God is a pretty good tear jerker.