Aichallenge-tron is a project mainly written in C#, it's free.
Google AI Challenge
To compile on windows: 1, get at least C# Express 2008 2, open bill_ai.csproj 3, build
Follow instructions here to get the offline engine: http://csclub.uwaterloo.ca/contest/strategy.php
Competition summary: http://www.benzedrine.cx/tron/
Rank: 52