Automatic water dispenser
You put empty buckets in the top, water buckets come out the bottom.
Day/Night - Input
This construction can be used to camouflage a cave entrance that is only visible at night (or during the day).
Above-ground redstone line (cf. power line)
A variation of the power line: the redstone line is built on barriers.
Automatic animal killing machine
This machine helps in killing animals to get the items quickly.
Lantern with Nether Portals
A lantern for a large city. You can switch to nether portal light and to redstone lights.