For the uninitiated, Katawa Shoujo is quite possibly the best Visual Novel known to man. It is... no, I can't do that. I can't describe its feels truly. So I'll try with less formal words.
OH MY GOD WHY AREN'T YOU PLAYING IT MY EYEBALLS STILL BURN FROM THE TWO YEAR BREAK I'VE TAKEN FROM IT. Jesus Christ it's good. It makes you into a better person.
The premise is that you are Hisao, who gets sent to a school for people with problems that make daily life difficult. There are girls. Five of them for you to fall in love with. Each arc fills your heart with a molten ball of pain that, upon its finishing, expands to make your entire heart into a priceless piece of gold.
You will fall in love, and you will cry.
There are some NSFW scenes, but you can toggle them off via the options menu.
Please, don't deny yourself this amazing experience, people.
http://www.katawa-shoujo.com/download.php
Full version. Go. NOW.
EDIT: After reading Andrew's post above... I think I'm going to go get some exercise.