Dear Yuletide Author...
First off, thank you for whatever fic you'll be writing. I promise, no matter what it is, I'll be grateful. I realize that you may or may not be a slash fan, so feel free to convert any idea into a gen piece. Most of the ideas listed below should be general enough to work either way. I'll read (almost) anything, though I'm not big into femmeslash or het fandoms, and obviously slash is preferred though I'm not picky about level of detail. Explicit is great, anything less than that is wonderful too.
I like: snark, banter, teasing dialogue, witty humor, domesticity, geeks, sex with plot, sex with only vague plot, sex without plot, threesomes, moresomes, kink, sword-fighting, tentacles, ukes in distress, hurt/comfort
I'm not overly fond of: excessive weapiness, overly feminised males, songfics, things involving bodily excretions of any type including heavy blood play, weak-willed characters, drug use, shota/underage sex
Now, for more detail on the specific fandoms.
Hellboy
Nuada/John Myers or Hellboy/John Myers or John-centric gen
Anything slashy involving Myers would make me happy. I'm of fan of Nuada/Myers (or Hellboy/Myers) but anything'll make me happy. What if Nuada hadn't died? What if the elves had never warred with humanity but instead kept their power and integrated into society, possibly as a ruling class? (I would prefer not to see degraded/subservient class for the elves, but I'd be fine with humanity put in that position.) What if John hadn't been sent to Antarctica? What if Nuada survives and ends up in Antarctica with Myers? What if Nuada was recruited to work for the BRPD? Snark between any of the characters would be lovely.
John's my favorite character. Hands down. (Okay, so I like Hellboy a lot too, but for fic, it's all about John.) I really love Nuada and his angsty brooding loveliness. John and Nuada are such a niche pairing, (there's like three fics for it, one of which I wrote) that I'd love to see more for them. I'd be totally good with an AU for this (since, well it has to be at least a little altered from the cannon to work at all) so if AUs are your thing, go wild, though I'd like it if at least a little of Nuada's divinity stuck around. I really like the fact that he's a Celtic god wandering around in the human world. The whole mythology with the Tuatha de Danna and Nuada and all of that is fascinating, so if you want to work that in, feel free. Pretty much anything goes with this prompt.
Fairy Tales
Any
I love slashy takes on fairy tales. Doesn't have to be heavy on the romance if that's not your thing. I'd be happy with pretty much anything fairy tale-esque, but a good fairy tale gay romance would make me soooo happy.
I'm a big fan of fairy tales. If you need particular inspiration, I really like new takes on obscure Grimm tales, foreign mythology (esp Japanese), or the classics - Cinderella, Sleeping Beauty, Snow White, Legend of Sleepy Hollow. Fairy tale elements that I'm fond of are dragons, fairies, good triumphing over evil, power hidden in an overlooked form, tricksters, wolves/coyotes, ravens, scarecrows, snakes, spiders, changelings, oni, kami.
Star Trek: Deep Space Nine
Garak/Bashir or Bashir-centric gen
Anything with Garak and Bashir interacting would make me happy. Doesn't have to be slash, though that would be brilliant. I'd love to see something focusing on cultural and personal differences between human and cardassian - society, physiology, cuisine, customs. Seeing Bashir trying to acclimate himself on Cardassia would be neat.
I adore Bashir. He's my favorite character in the series, and the interaction between him and Garak is just delicious. The actor for Garak was actually pushing for the gay subtext but it wasn't allowed into the script, though it still shows through in his actions.
Cable and Deadpool
Cable/Deadpool or Deadpool-centric shenanigans
Anything with Cable and Deadpool, possibly porny, possibly just Deadpool getting up to his usual shenanigans. Bonus points for explosions, metahumor, and Deadpool getting killed at least once.