|X-Com: UFO Defense (Also known as X-Com: Enemy Unknown)|
Use of Procedural Content Generation Methods
X-Com: UFO Defense uses a random level generator to generate the sites investigated by the player: either UFO crash sites, UFO landings or locations terrorized by aliens. The sites are generated by aggregating a set of prefabricated terrain patches together to form the map, with the available terrain being determined by where on the globe the event is (such as urban, desert, or jungle environments). Through the same mechanism the structure of the base that the player designs in the strategic portion of the game being becomes the tactical map in the case of an attack on that base, even though the player may not have thought of the defensibility when placing the base facilities (almost a form of user mediated content) It includes a form of interactivity rare in more modern games: the destruction walls, doors, hills, and other terrain.
An open source remake of this game, UFO: Alien Invasion is an interesting example of limited PCG married with an FPS engine (a modified Quake 2 engine). Apart of random maps constructed from 3d models (in various stages of brokenness in most versions) they have randomly generated (but according to life-like rules) alien teams (number, position, alien stats, equipment) based on map kind and game stage. The latter, together with fancy AI that makes use of the equipment, makes fixed maps less predictable.
X-COM: UFO Defense - Wikipedia entry for X-COM: UFO Defense.