Best printable puzzles to 3d print?

Any puzzle made by Oskar van Deventer. He's got a ton of them, they're all free, and he posts YouTube videos about them all

We really like this treasure chest https://www.printables.com/model/206656-treasure-chest-puzzle-box-update. Mechanism works very well and children were exited when solving the puzzle (as present box). There is even a video with its maker showing the variations and explains the unlock mechanism.