First off, let me say that the fact that you're writing me a story is literally going to make my Christmas so please don't feel too stressed, as long as you enjoy writing whatever you write then I'm sure I'll love reading it.
There are things I like in fic: first times, happy endings, angst with happy endings, schmoop with happy endings (are you sensing a pattern?), obliviousness, pining, slow reveals and best friends. I have a thing for seeing how relationships are viewed by people outside of the pairing, and I like the things people show but don't say.
There are things I don't like in fic: unhappy endings, death and non-con. I also don't like humiliation or character-bashing (not that I think you'd do that!) and I have an embarrassment squick a mile wide.
I'm fine with porn or no porn, whatever you're more comfortable with. I'd like slash but I'd be happy with gen.
Now, some specifics:
Tanya Huff - Blood and Smoke series (Lee Nicholas, Tony Foster) - the world needs more Lee/Tony stories! I'd love to see a story where Lee comes out/is outed and how they handle that. I have a secret wish to see what would happen if Lee ever met Vicki and Mike, or what happens when Tony meets Lee's family as his boyfriend (it says in book one that he's already met Lee's mom on set). Or just some plain old demon fighting and magic would rock too!
M Chandler - Shadow of the Templar (Simon Drake, Jeremy Archer) - I'm so excited to see this as an option! I love Jeremy and I love Simon and I love how they're in love without ever needing to say it. I'd love something set after the last book, maybe the next time they meet up or maybe the next time Simon has to let Jeremy get involved with a case. I also love the rest of Simon's team and would love to see them and how they react to now knowing about Jeremy and Simon's relationship.
W E Johns - Biggles series (James 'Biggles' Bigglesworth, Algy Lacey) - okay, firstly, if you signed up for Biggles thinking 'aw, yay, books from my childhood' and you're not comfortable slashing it then, seriously, GEN IS FINE. I love the period between the wars when they've just found Ginger and they're having fun being young and going on adventures. I love the Biggles/Algy relationship and I'd like to see that explored.
Live Free or Die Hard (John McClane, Matt Farrell) - ANYTHING AT ALL. I'd love to see Matt meeting Holly and Jack (please no bashing! Holly is a fantastic lady), or Matt meeting the people John works with. Or just some dating/first-time fic would also be lovely.
In conclusion, THANK YOU for writing me a fic. I love you already.