Super Simple:
This is called the Q-drum and it's built for transporting 20 gallons of water - something that millions do everyday. Super simple indeed.
You can read more in the New York Times article Design that Solves Problems for the Worlds Poor. I first heard about the Q-drum from Darren Barefoot.
Needlessly Complex:
This is a Japanese toilet that has 17 buttons. The one I use at home only has a single lever and it's never left me wanting more. Needlessly complex? I say yes.
Maybe you've seen similar items? I'd love to hear about any products that are stark examples of simplicity or complexity.