There is a possible gaming application that I would gnaw off my own leg to get my hands on. I'll describe it, here.

This app would be a mapping utility. You could create maps with it. Topological maps of continents, mostly, with cities, roads, forests, rivers, etc. Tracking other information, like mineral deposit locations, would also be pleasant.

To generate such a map, I could ask the program to generate a random continent, a random group of continents, or, given a rough outline of a continent, fill in the general shape of a continent.

Then, with a few mouse clicks, it could randomly place forests, rivers, towns and roads, etc.

Then, I could edit this data, adding new cities, adjusting the shape of roads between cities, adding new mineral deposits, etc.

To change the shape of the land, I could use normal CAD-like tools, like splines and node dragging, or use natural phenomenon to shape my land. For example, I could tell the application about a new fault line, force it to run through a bunch of history, and mountains would soar up. An asteroid crashed here? No problem: tell the app the size and composition, and it'll level trees, incite volcanoes to form, create new mineral deposits, etc.

In the end, various maps could be rendered, including 3D flybys, traditional atlas-style maps, and Tolkein-esque maps (including map distortion, if required)

Already, I've wet myself in anticipation (and it's even reasonable to write it!) A few more (less reasonable) features would make it even more phenomenal, however.

Economy generation (Where are things mined? Where are the population centers? Where are the trade routes? Make up random encounter tables of roads, based on likely travellers (farmers with grain, miners with ore)).

Calculating (given prevailing winds, etc), average rainfall maps, where the best cropland is likely to be, etc.

Tying data to the map.

Mapping buildings, as well, and placing them on the map. (in 3D!)

Civilization generation (lots of forest? elven nation added). This would be fun, although difficult, to automate: one could go so far as to determine where civil wars are likely to happen, based on randomness, as well as racial animosities (configurable by the user, of course)

Specification of user-determined data. For example, I care a lot about the regional influence of various gods in the campaign world. No mapping utility, I understand, will give this to me. On the other hand, I can imagine such a utility letting me place entities that looked a lot like political boundaries, but on a different map 'level', and just *state* that these boundaries are for religious zones.

Ah well. It's a dream, anyway. One day, I might even do it, but I still have to finish Moksa first.

Oh yes: if it were open source, it would be very popular. Probably make somebody's career.