Anchorhead

Michael Gentry's Anchorhead is very good horror IF; the author has a nice feel for the challenges posed by the genre, and the game is consistently both scary and playable, no small feat.

What really makes Anchorhead shine, though, is that storytelling and gameplay don't exist alongside each other, as it happens so often in the genre. The puzzles complement the story, they are embedded within. No puzzle ever feels like it has been created as a pure obstacle to slow the player's progress - it all seems very natural. And this is something only very few games (commercial and non-commercial) can claim of themselves.