To get the ball rolling, here are some of my own observational picks:
There’s no denying that Outside BOX probably had the most audacious puzzle gimmick of needing to tinker with the game files!
Lurking Lapine sought to elevate the stealth-platforming experience with some neat and ambitious features. Being able to dig rabbit holes to warp about the level I found to be a cool feature.
With Weight, when do I Hibernate? I found the idea of needing to build up your stats in order to tear them down to further your weight gain a really interesting approach to the theme!
Finally, despite some camera issues, Greedy Gigs should get a mention for its ambitious 3d parkour/spider-man traversal antics!