OpenTTD

OpenTTD is an open-source clone of the MicroProse game "Transport Tycoon Deluxe", a popular game originally written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features. In the game, you are the head of a Transportation Company, and your job is create the best transportation system for the simulated cities and industries, and make more money than your competitors.

OpenTTD can download open-source replacements for the graphics (OpenGFX), sound effects (OpenSFX) and music (OpenMSX), or it can copy the original assets from the CD-ROM of Transport Tycoon Deluxe.