Lots of books have made me cry, and I don't cry easily.
I echo "The Road." Excellent book, although I had to start it twice before I got into it.
Others that made me cry include:
"True Crime," in which an innocent man prepares for his execution as well as he can while a compromised reporter realizes quite late he couldn't have done the crime.
"Of Mice and Men," in which itinerant farm workers during the Great Depression do what they can to protect one another from the world's cruelties. (A generation later, my kid was reading this in a doctor's waiting room and started to cry.)
"To Kill a Mockingbird," more than once, even.
"The Velveteen Rabbit," which I read to our kids when they were little, and cried nearly every time, to their amusement, about how toys become real when they are truly loved and stay that way once forgotten.
"Angela's Ashes," about growing up extremely poor in Ireland, your father a drunk, your mother doing the best she can, which is barely squeaking by.
"Room," about a kidnapped teen made pregnant by her captor, trying to raise him as well as she can in the room where they're being held.
There are a whole lot of books from the YA market that dozens of websites share as tear-inducing but that I haven't read: The Kite Runner, Extremely Loud and Incredibly Close, Me Before You, The Book Thief, The Bluest Eye, My Sister's Keeper, The Art of Racing in the Rain, and more.