I made a fantasy card game loosely based on Crazy Eights (the game Uno is based on) called Crazier Eights. Every card can be played for an effect. It is now up for sale. Go here if you would like to buy a copy. I also put up a print & play version of the Alternate Edition prototype, which can be found here.
I also made two spoilers, which shows all the cards used in two different versions of Crazier Eights: