1) Clannad (for being a humorous and great novel)
2) Ever 17 (impossible for this to not be here)
3)
Fate/Stay Night Narcissu(Oh man, the tears keep on coming...)
4) Sharin no Kuni, Himawari no Shoujo (Man, the protagonist is damn badass)
5)
Sekien no Inganock Higurashi no Naku Koro Ni (It seems mystery novels are better)
EDIT : I've reached the 40s mark and my list changed again.
Worth checking out and (some partly) translated:
ChaoS;hEAD, Tsukihime, Fate Stay Night, Sekien no Inganock, Symphonic Rain, Utawarerumono, Remember 11 (more mindfuck than Ever 17), Eien no Aselia, School Days, All Key's works, ef~a fairy tale of the two, edelweiss