I stumbled upon this beautiful MOC on Brickshelf yesterday - a model of Cape Blanco Lighthouse by mrjasonvv. My favorite technique in this MOC is the construction of the roof. Yes, it is just ordinary slopes used like slopes usually are, but notice that they are all 1x2's - it gives a very convincing clay tile or shingle effect.
Notice the 1x1 round plates at the edge of the roof and the 1x2 curved bricks incorporated in the ridge pole. Oh, and don't miss the clever SNOT door!
EDIT: those are NOT 1x2 slopes, they are 1x2 tiles mounted on a 45 degree angle! How did he do that? Also notice the roof of the tower - it is constructed much the same way.