Dvorak is a card game where all of the cards start out blank. Players choose a theme, make up enough cards to get started, shuffle and deal, and start playing. If anyone has a good idea for a card during the game, it gets shuffled into the deck.
You can use the Dvorak system as a skeleton for making a solid and standalone card game, you can play it as an experimental or cut-throat Nomic, you can use it to kill half an hour drawing pictures and forcing your friends to perform forfeits, you can throw together a card game based on your favourite film or sport or in-joke, or you can even build your own collectible card game from the ground up.