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
-1000000000000
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)