1. Doctor Who Classic: 5th Doctor, Tegan, Nyssa and Adric were personally my favorite grouping during the series. I do prefer 5 and Nyssa in a romantic pairing, since I think they have the most chemistry. However I do imagine that Adric may have a cute crush on Nyssa due to her intelligence. Tegan I think functions as the sort of older sister of the group, protective of her friends rather than a romantic interest. However I can see her in a relationship with Nyssa. I'd be interested in either a romantic fluff or just a fun moment with the TARDIS crew.
2. New Who: I just really want something featuring Oswin. I absolutely LOVED her character in Asylum. I am game for just about anything with her.
3. Star Trek: Okay...I am NOT a Spock/Kirk shipper. I think they are great and close friends but I can't see them in a working relationship. Spock and McCoy however...I can totally see in a romantic pairing. I'm not exactly sure how that could come about, but I'd be willing to read it whether it be a long term thing or a short romantic tryst.
4. Farscape: I ADORE Farscape! Zhann is my FAVORITE character and I hated that she left. I would really like to see a fic centering on her. I'd like to see her perspective of things that happen on Moya. Maybe an introspective on the path her faith has taken?
Hope this helps!!