Chances are you've played a first-person shooter such as Unreal Tournament, and if so chances are you've come across what is known as a bot. Now these things can be really annoying, that is unless you are behind one. Andy Sterland, James Lissiak, and Tom Randell has created an .Net C# or VB bot system for Unreal Tournament. A bot needs to have some artifical intelligence (AI) to be effective. They created a project template, a bot API and a visualizer so you can watch people go up against your bot while you're eating some popcorn.
Soapbox has a video of their AI efforts.