Some personal examples:
Dice forge has its way of handling dices that felt incredibly smart the first time I played it
Same for Codex Naturalis, I was impressed by the simple way they printed the cards to allow for modularity, obviously the game is a lot simpler than I thought but it gave me some interesting ideas with how to overlap cards
Or the boards in Fort that have this double layer so that you can nest your pizzas and toys in there, so cozy!
My playground really enjoyed that in Artisans of Splendent Vale, the Harinya meeple fits nicely on top of the doggo meeple. Then the player unlocked the ::: spoiler Tag Along ::: power that ::: spoiler lets Harinya move whenever the doggo moves ::: so the fact that they fit together is actually ludologically relevant