Re: Welcome! :-D
I've been thinking on & off about why I DON'T have a favorite Slytherin pairing... (me, obsessive? - what makes you think that?)
And I think that it is because although I can't actually think of a single Slytherin characteristic within myself, I do admire & enjoy some Slytherin characteristics in others - ruthlessness, pragmaticism & ambition.
I mean, look at bravery - there's that Gryffindor bravery, like Prof McGonagall, racing out in the night to confront those unjustly harassing Hagrid (OotP) & I LOVE that, I can relate to that, that impetuous nobility, that sees a wrong & propels into action. But what does it accomplish? And then there's the Slytherin bravery - if Snape had decided to act to save Hagrid, it probably wouldn't have been as flashy & noble, but it would have been SUCCESSFUL! And somehow I can't picture myself there, even though I admire it.
Hence my favorite pairings are all about a Slytherin & some-one other - not-Slytherin: sort of a reflection of myself & my likes. So, maybe that's why Severus/Remus, or Draco/Harry, or my latest obsession, Millicent/Rosmerta, does it for me.