Some people prefer the infamous floating Volkswagen ad; for others, it's the legendary "If you don't buy this magazine, we'll kill this dog" cover.
But for me, I think it will always be "The Miracle Monopoly Cheating Kit," by Christopher Cerf, from Issue #38 (May, 1973) of National Lampoon -- the "Fraud" issue.
It was inspired. Because sometimes capitalism needs -- you know -- a little help. A little nudge forward. An edge.
The kit contained deeds for fake properties, which could be mortgaged for quick cash or used as trading stock in real estate swaps (in this, the MMCK was a quarter-century ahead of the game).
All of these hacks were printed on authentic paper and card stock, using the right fonts and ink colors. The MMCK even included an extra double-sided page of rules (justifying the gambits above, plus many more, for the would-be Master of the Universe) that would slip, undetectable, into the rule booklet provided with the game -- because control over the regulatory environment is also necessary for capitalism to flourish.
The kit also offered tips on such important matters as how to palm cards and slip them onto the Chance and Community Chest piles, as well as distraction techniques to cover moving larger forgeries on and off the board.
My favorite cheat: The "Shoot the Moon" card, a Chance card (or maybe Community Chest -- alas, I can't find an image anywhere) that, when drawn, immediately turned the game into a race to see which player could go bankrupt first. It was a handy way to turn a bad situation to one's advantage, and once again a nice foretaste of 21st century change-the-rules capitalism.
(And, while this doesn't have anything specifically to do with either fraud or Crime Week, here's the pewter penguin I like to bring out as my token in Monopoly while the other players are still squabbling over the cannon and the race car. Heh.)