Yeah, I really like Severus/Regulus too. I think I have yet to read another fanfic of them, but between the two of them (plus Lucius and all the Gryffindors) there is *so* much unexplored complexity, and so many possibilities in the dynamic of their relationship with (or not with) each other, that it's very compelling.
(May you and I never have to watch our loved ones repeatedly almost kill themselves.)