It's only my opinion based on the puzzles that I have played with. I cannot comment on the puzzles I have never played with and hence I may miss nice puzzles in the list.
The order of the puzzles does not mean that the first one is the best.
1. Angel box by Wil Strijbos
One of the best example of the sequencial discovery puzzle.
Many steps, many tools to free the angel. A challenging puzzle!
But take care not to loose tools (yes you can...)
2. Pachinko box by Wil Strijbos
In my mind the second best Strijbos puzzle. Many steps, and unexpected ones as well. You have to get the 2 coins to solve completely the puzzle.
3. Lotus by Wil Strijbos
The puzzle is solved when you understand the name of it... ;)
Tools can be lost. Tools can fly out. Take care!
4. First box by Strijbos
A pretty heavy box that has its secrets. Make the puzzle smile!
5. Big Ben by Brian Young
6. Houdini torture cell by Brian Young
7. Butterfly by Wil Strijbos
Big puzzle, but this time you will have to deal with a massive lock. Analyze the puzzle carefully or you will jam your puzzle and beg for help (and external tools) ;)
8. Packman by Gary Foshee
9. Gary's escape by Gary Foshee
Free the marble!
10. Open lock by Gary Foshee
Nice lock. Seeing the inside does not mean you will find right now the solution :)