Bill Dembski, at Uncommon Descent, has a few days to run on a competition to demonstrate gradual development/co-option in the technological realm.
When I had a connection with the RAF, they had standard issue sunglasses which were known as "Mark 14's". What interested me about this was how something as inherently simple conceptually as sunglasses should have gone through 13 previous design iterations prior to arriving at its current state of sophistication. It led me to construct stories akin to the evolutionary just-so stories that people suggest in nature as to what, exactly, the previous 13 "marks" might have looked like. For example, I wondered whether Mark 6's had been abandoned when they ripped off the ears of a fast jet pilot who ejected when wearing them, on account of the fact that the arms of the glasses were made out of cast iron and weighed five kilograms each. Or whether the primitive Mark 3's had been rejected when it was determined that plywood, although cheap, didn't make acceptable lenses for sunglasses.