I stick pretty closely to my preferred pairings: Spike/Angel or Spike/Connor (Jossverse), Jack/John or Owen/Gwen (Torchwood), David/Jack (Kings), Brian/Justin (QaF), JM/VK or JM/GDL (RPS), occasionally House/Wilson (House). I'll give other pairings a try, if it's a writer I really like; but even then, it's pretty rare.