1. Apocalypses I'm not sure why this grabs my fancy but it always does. I'm less a fan of the lawless-society trope though I am happy to read a splintered society one. The apocalypses that really make be happy are those on a biblical level. Surreal, supernatural, and all-consuming are all bonuses. Stephen King's 'The Mist' where there may, or may not, be any place left on the planet free of the monsters; and various zombie apocalypses are the more obvious versions. I think it's because the attention is kept strictly personal, on a group of individuals finding hope in an essentially hopeless situation. I'm also, sadly, a fan of the logistics of being a survivalist. How do they get enough food, medicine, water, and other supplies? How do they barricade themselves in? Where?
2. Voyeurism One thing that makes me a fan of both video games and apocalypse daydreams is the idea of being able to walk into people's homes just to see what it looks like. Yes, I'm weird. What wannabe author isn't? I'm curious about places and the histories of those places. Even boring places. What does a cement factory look like? A police station? What is that electrical cabinet actually called? What does a fantasy mill look like? Most people skip the details entirely, for fear of getting it wrong, or of bogging down the text. You don't need to feed me a lot to keep me happy. Just a few dribs and drabs. The correct name for a particular room, a protagonist leaned up against an oil drum, the correct terminology for items and equipment (though you might need to carefully use this in context for those who aren't as scholarly.
3. Natural Disasters Especially tornadoes. Did you know that every few years I have a dream about tornadoes? Either running away from them, helping evacuate people to safety, normally ending with me hiding in a dirt tunnel underground. I never get scared in these dreams. Just filled with a sense of awe and wonder. It helps that I'm unlikely to ever see one in Australia. It's not just tornadoes that fascinate me. Hurricanes, bush fires, earth quakes, etc. It's not enough to simply have it happen. I want to see how people prepare to one, how it impacts the world in its wake, and how people adapt to it afterwards. I want to see the little details. I want to understand it.
4. Moral Gray-Scale. As painful as it is, I like being able to understand the twisted depths of all the characters. Their justifications are often more interesting, and painful to read about, than showing them cackle manically while torching orphanages.
5. Causing pain to a loved one. I can watch a dozen horror movies about serial killers and monsters devouring people but I still flinch when I see a friend perform necessary amputations without anaesthetic. Its a fate many have suffered, something I can imagine might happen to myself, and I can more easily relate to both victims (as the poor fool with the saw must feel pretty bad as well).
6. Evil for a good cause. There's a reason why the cults in the Project Zero series (videogames) were far more fascinating than the ones in most others. They did terrible, horrible things, often to willing participants, to keep something worse from happening. It's not enough for them to simply think it's for 'the greater good', but when it truly is, it's horrifying.
7. Symbolism. Much in horror benefits from good symbolism. Humans think and feel in symbols. A nightmare world that shifts according to its master's needs / sins / desires. A monster that reflects some of humanity's greatest fears in its physiology (i.e. werewolves reflect loss of control, vampires used to reflect fear of contamination).
8. Struggling against one's inner nature. A demon fighting against its sinful nature. A monster seeking redemption. A man struggling against his cursed heritage. Someone seeking to overthrow their abusive histories to break the cycle of violence. I'm not as much of a fan of people hiding from their pasts, though. People who have chosen, off their own back, to do evil and then changed their mind or were redeemed or whatever. I don't hate this plot arc. I'm just not attracted to these plots.
9. The survivor. Y'know that character, normally a minor one, that goes through hell and back and survives a massive beating? I love that character. I will root for that character. Once a character has survived enough, they really should be allowed to live.
10. Ships. Ever since I started reading nautical fiction, both fantasy ones - Robin Hobb's The Liveship Traders - and various Napoleon-era historical ones, I've become a sucker for anything on a ship.
11. Underwater stuff. I think the ocean is one big, unexplored mass of brightly colored things that can kill you. What's not to love? Describe it well enough to make me feel like I'm there and I'll love it.
12. Connected Protagonists, preferably with a younger sister or child. I don't mind an orphan protagonist but I find it hard to relate to an orphan that's got no real responsibilities to their attachments. Normally such relatives are just a chapter one issue that chapter two will sort out. I think that's a shame. Y'know what's got more conflicts and trouble than looking out for yourself (and you're well-armed, well-equipped compatriots)? Having to raise your younger sibling or kid friend or what-not! The movies made me a sucker for it (Grave of the Fireflies, for example).
13. Ghosts, zombies, and other undead things. What can I say? I like them. They're creepy as sin. I think it's just because I'm stubborn so I appreciate stubbornness. What's more stubborn than refusing to die? Also, genres involving the undead often do quite well with tragedy. I draw the line at vampiric angst, however. It's more tragic when people are trying to make the best of a bad situation, in my opinion, rather than brooding about something that happened decades ago.
14. Demons, hell, and embodiments of sin. This is partly due to number 8. Struggling against one's inner evil; and no. 7 symbolism. I'm not as much of a fan of the religious hell of fire and pain. I prefer a more personalized form of hell, such as can be found in the classic novel, Dante's Inferno. Dante used symbolic representations of fitting punishments for sin quite well. Even demons that are flat-out evil also work well as monsters - they're ancient beings who have reason to truly despise us. How is that not going to be a problem?
15. Culture Shocks. Nothing highlights how a culture works more than when two cultures collide. Even in a peaceful encounter, the differences between how they meet and greet, do business, and date can be quite interesting. This goes doubly for fantasy worlds - particularly those where most people rarely leave their village.
So, that's a list of basics that attract me irrationally to a tale. What about the rest of you? Feel tempted to try it out?