I'm really impressed with Omer Arbel and Corrine Hunt's design for the 2010 Olympic medals in Vancouver:
All the medals are unique and different from one another but share an image from the same piece of art. I like this as it creates a bigger picture and makes the medals far more rewarding than a mass produced coin.
What impresses me the most is that all the medals are made from e-waste. The quality they got by recycling parts of computers and mobile phones is inspiring.
There is a great video on Core77's blogger page describing this further.