#2 (Block and Key): An interesting key puzzle with the added use of nails to create a not too quick nor not too long puzzle.
#9 (Repair the Maze 2.0): I like the evolution of the original, but it is far too big.
#19 (It Only Gets Worse): I have always liked this level for its theme of gradually extending the dodging part and its overall mechanism works fantastically.
#22 (Pneumatic Diversity Vents): The concept is fresh and the level features variety.
#23 (Toggle Path): An interesting and unique maze.
#27 (Blue Ridge Corporate Center): I like the theme of this level and the use of cloning machines and the rooms within the overall "level space" fit nicely.
#30 (Anomalous Materials): This seems like another "progress ball" level, but the use of sokobans to advance further is a nice touch and keeps this level above most sokoban-themed levels so far.
#33 (Precipitous Elevation): Something about this level sticks out to me. I've never seen anything quite like it and there's not much to say about it, but I enjoyed it a lot compared to the other levels in this pack.
#37 (Deflection): I don't necessarily want to praise my own levels, but I feel this level could serve as an interesting breather level somewhere. It could be considered as an interesting mini-challenge.
#42 (It's Easy Being Green): Looking at this level from a distance, it appears to be a twist on the idea of being forced into picking up an item at the beginning that prevents you from immediately exiting, but in this case, the green key then allows you to perform certain actions instead of simply being denied access to the exit. The puzzle is nicely sized and the level is quite fun to solve.
#43 (Blox): This level's concept is very interesting and doesn't seem to be heavily used. The puzzle isn't overwhelming, but is decently challenging.
#47 (Snow Patrol): There were one too many ice mazes in this pack, but this one stood out the most. It provided a challenge and, for its size, still retained a "lost" factor (as J.B. mentioned), whereas in most of the other ice levels I played, I wasn't really enjoying the level. The teleporters also add to the level in a good way that I can't quite describe.
#50 (Launch the Bacon): Probably the "blob level" that I'd want to see get in the final levelset.