^ What all have you seen? It helps if you list a few shows that you have seen
Well anyway, here goes,
Clannad &
Clannad After Story
Blood+ - Romance with a dark theme.
RomeoXJuliet - The name should be enough I think.
Ah! My Goddess - I think this should be perfect for you.
Eureka - Romance and Mecha.
If like any of those then I'll suggest some more