I've written a simple AI for openttd, called BorkAI.
It's a truck-only AI that creates routes between industries and to towns (but not passengers or mail).
As the proud product of a couple of weeks of trying to learn the NoAI frameworks, it sports
the following features (yes, features, not bugs
* slow-as-hell pathfinder. Abusing the RoadPathfinder isn't the best option, and it shows on big maps,
when it can get literally stuck. It's still fine on small ones though.
* approximate estimation of number of trucks needed. Expecially when competing with others, or transporting hundreds of
goods from factories. Prepare for a few traffic jams
* Bad NewGRF support. Shouldn't crash, but because of some assumptions won't work very well in a non
Well it has a few *nice* features also
* Does most of the things needed to survive: renewing trucks when they get old, upgrading to faster ones, handling of economy changes (industries appearing/disappearing).
* It's eco-friendly. Try not to build unneeded roads. Actually this is a tunable so you can force it to build the absolute minimum of road required to get from one
place to the other. Nice when playing against it. Or you can let it build as much road as needed to the shortest route available.
* In fact, on the small maps, it's more or less competitive with the other AIs. It won't die easily.
Any feedback is welcome, expecially from someone playing against it (I don't like to play against an AI), or using any kind of customization.