I am quite picky. The bottom line?
MUST BE YAOI/SLASH.
Anything else I have difficulty getting into.
The only exception to this is for Eragon. I'll read anything with Oromis in it. Or actually, anything at all. The world needs more Eragon fic.
Preferred pairings are as follows:
For FullMetal Alchemist:
Ed/Envy (FMA OTP)
Lord of the Rings/Silmarillion:
Thranduil/Elrond (LotR OTP)
(Really, I love any elfslash!)
Crowley/Aziraphale (Good Omens OTP)
Last Herald Mage:
Starwind/Moondance (LHM OTP, definetely what I write most.)
Anthony/Johanna (A hetero pairing that I like, le gasp)
I will read ANYTHING for Petshop of Horrors (slash is preferable) and Alexander (the fandom in which slash is expected). I will also read anything with slash for Earthian.
For Mercedes Lackey, I've only read The Last Herald Mage trilogy, so far (though I hope to remedy that).
And I ADORE mpreg. Love it!