Buy negative land.
[Santa Paravia computer game (1979)]
Santa Paravia was like a text-based Sim City created for the TRS-80 computer and later ported to many other computers (one person ported it back to the TRS-80, not realizing that the original version came from there). You role-played as a 15th century Italian city-state ruler, and your objective was to become king or queen before keeling over from typhoid or the like. The game progressed as a series of turns, and each time you were given an option to make fiscal decisions for your peoples:
1. BUY GRAIN 2. SELL GRAIN 3. BUY LAND 4. SELL LAND
Eventually some wiseacre figured out that there was a tiny bug in the game that allowed you to purchase negative land.
HOW MANY HECTARES DO YOU WANT TO BUY
This, if memory serves, caused your florin count to shoot through the roof, and from there it only took a couple of turns to become royalty. Used when asked for stock tips or similar financial transations.
– Jeff Stendec (2005)