I'll edit it when I think of more.
"You only exist inside the people who are aware of your existence." - Lain (Serial Experiments Lain) << I think Lain says it. It might actually be her father.
"Akari~n" - a bunch of characters (Yuru Yuri)
Then there's these from Clannad After Story
(they're in spoilers for a reason):
I just wrote what it said from the subs.
Tomoya: Ushio. We might not be able to find that robot. We can't do anything about it. So let's buy another one. Okay?
Ushio: There's only one.
Tomoya: There we lots of them at the store.
Ushio: It's the one you chose and bought for me.
Tomoya: Eh?
Ushio: First thing from papa.
Sad music starts playing.
Tomoya: Ushio. Were you lonely?
Ushio: Mm.
Tomoya: Was it fun to come on a trip with me?
Ushio: Mm.
Tomoya: I see. Ushio... would it be alright if I stayed with you? I've been a bad papa for many years, but I'll do my best for you from now on. So, would it be alright if I stayed with you?
Ushio: Mm.
Tomoya: Really?
Ushio: I want you to be with me.
Tomoya: I see.
Ushio: But today, I lost an important thing, so I'm sad. Papa... You know... Is it alright not to hold it in anymore? Sanae-san told me, places I can cry are in the bathroom... and in Papa's arms.
Tomoya: Mm. Mm!
They embrace each other, cry and the music gets even sadder.
Tomoya: I'm sorry... I'm sorry.
Straight after that scene I just wrote when Tomoya and Ushio get on the train and he tells Ushio about Nagisa, when he breaks down and says her name it just tears me apart.
"Nagisa... Nagisa..." - Tomoya