Castaway's one of 'em. Can't think of any more at the moment but I know there are more...
There was this one book I read as a child that was about a kid who loses her grandfather, it was sooooo sad... Then there was
The Giving Tree, and
Are You My Mother? (don't know why that one made me sad, something about the baby bird looking for his mother but not being able to find her and instead running into all these cold, lifeless man-made machines like forklifts. lol, weird).
In middle school they read us a book about a homeless kid who lived in a box in an alley or something, these cruel children tormented him by holding his eye open under a soap dispenser and pumping it, and they killed his only friend in the world - a scruffy stray cat that was missing an eye
When I found out they killed his cat, oh man... I can still recall how it made me felt more than the details. What an awful book to read to children.
Edit: here it is:
http://cimages.swap.com/images/books/53/0440442753.jpg
Guess he didn't live in a box. And maybe the cat wasn't missing an eye? Or maybe the cruel kids poked it out or something. I got some of the details right at least ;P This post is getting way too long.