I didn't think the mechanic was impressive, but fortunately it was in the right hands. The puzzles are very well done, and the "latter phase" of the game is beautiful.
Braid
Time shenanigan are always nice. Though I'm not sure how well the puzzles hold up today in my eyes.
The Case of the Golden Idol
This was really nice. The deductions and ahas are nice like in Obra Dinn, but it's also overall a different experience that can stand on its own.
Machinarium
The Misadventures of P.B. Winterbottom
Myst III: Exile
Outer Wilds
This was certainly an experience. I love games with "organic" puzzles.
Portal
Portal 2
Return of the Obra Dinn
A breath of fresh air.
Riven: The Sequel to Myst
The Sekimeiya: Spun Glass
please play this holy fuck
Snakebird
The only good mobile puzzle game. It is high on this list for being able to achieve good-puzzle-game status on such a platform. Kudos.