My trickiest redstone circuit was not very complex but it was a nice problem solving thing.
Idea was : How to raise a wall of sand, without using a "quick put a bloc under the sand before it falls down" trick.
My solution was to use two rotating solid blocs per column of sand that will carry the sand up.
My nicest designs are:
- A way to trigger things (doors/secret passages, lights) using a key (redstone torche).... or even a Disk in a jukebox
- A forcefield providing players to pass through
- And using a similar principle, a forcefield that allows players to go through, but not the mobs (not tested on the latest updates):p