The 2nd highest rated video in my collection is The Circle Center Granny Squares. Essentially, the granny square starts off being circular but ends up being a square. This has been used on several different patterns which include the Bumble Berry Afghan and Colour Burst Afghan Tutorials.
I think people get bored of the same old granny squares. This allows you have to some creativity but produce really nice ideas. I think Granny Squares are timeless as all that needs to change are the colours and not necessary the pattern. These and many more are featured at AllFreeCrochet.