18 is LOZ Majora's Mask?
As guessed by Farsala, my game #18 is The Legend of Zelda Majoras Mask.
Majoras Mask is a lot darker than the other Zelda titles. Which in itself makes it interesting. And although the basic gameplay is the same, because of you reliving the same three days, timing your actions and gathering masks makes it feel quite different.
As I never owned a N64 I played that game on the 3DS in the remake. Possibly this enhances the experience a bit, I wouldn't know. But it was just a great game. The masks add gameplay depth. In a way they are like items: you need the right mask for some puzzles. But it feels different, especially as you start out fused into one role.
Also, please do not forget that this game introduced Tingle.
Where would the Zelda-series be without him.