Portcullis (Castle Gate)

This is an amazing design for a large gate that actually opens and closes and I think you could probably use any kind of material you like for a door but the fence texture makes this very cool. The whole thing is surprisingly compact when you look at the size of the opening and it is reasonably fast as well. It is also a great introduction to triple pistons.

For reference, under the "floor" the controls go 5 bricks deep. The mechanisms could be easily hidden in pillars to either side of the gate.

Youtube Tutorial

Minecraft 1.5.1