One of my favourite games, and an influence on how I play, run and design others, is
Dead of Night by Andrew Kenrick: it's a deceptively simple horror game, which models movies & campfire tales excellently. It's not so much the rules of the game which do this but the meta-rules: the second edition contains extensive guidance on how to tweak the rules, adjusting variables and circumstantial effects to best reflect the style of horror game you want to emulate, whether that's dark horror comedy or tense, claustrophobic psychological thriller.
The nature of these meta-rules encourages experimentation and I've had some success playing with the possible combinations to produce different effects: my
Cold Fusion scenario, which appears in the book, changes the ways Survival point are used, splitting them into two colours which are drawn randomly from a bag, providing a countdown to a fate other than death for the player-characters.
I've also hacked the game more extensively, to profoundly change the assumptions of play, tailoring it to extended campaign play or ensemble disaster movies. Presented here is the essence of those two hacks, plus one more to represent tense, situational horror that can still be used in conjunction with 'humans vs. monsters' style games.