Ever played a game where you just can't figure out what to do, so you look it up? Then, when you discover the insanely obtuse solution, you're left speechless at your computer, thinking "How was I supposed to figure that out?" What are some game puzzle/level solutions so obtuse that there is no way a player could discover it on their own?
Forbidden Siren.
It has some deep moon logic adventure-game style. I think one character had to put a wet towel in a freezer, so that several chapters later another character could take the frozen towel, put a glass on top of it, and wait for the towel to melt to make the glass drop to distract a guard. There is nothing in the game that prompts you to do this, and yet if you don't, you will fail the mission where you have to distract that guard.