In 1982 McDonald's ran the Atari Scratch 'n Win promotion with giveaways of Atari computers and video game consoles. Hungry McDonald's patrons received a scratch card when they bought a large sandwich. Here's the lovely part:
Each game piece will be based on an Atari video game - Asteroids, Centipede, Missile Command, or Star Raiders - and can have a series of rub off spots. If you can match food or Atari game prizes without uncovering a "Zap" spot, you win.
What really strikes me about this promotion is how universally recognisable the Atari games had to be for people to understand the scratch cards. Admittedly, you wouldn't have to have played the games to do the actuall scratching, but the simple iconography of these titles were very well integrated into the cards, as in the case of the scratchable asteroids above.
I don't imagine it would be possible to do such a promotion with the more complex, visually realistic games of today. What would you scratch? Weighted companion cubes?