I'm a big fan of open clones of some of my old time favorite games like OpenTTD (I don't know how many hours I "invested" in Transportation Tycoon Deluxe...lol) and FreeCiv. Yet while they're open source, they really didn't fit to well here (where I try to focus more on managed language based projects).
Then I caught wind of another open clone project, but this one using C#...
OpenRA is a Libre/Free Real Time Strategy game engine supporting early Westwood games like Command & Conquer and Command & Conquer: Red Alert.
A few snaps of the game running;
I said the C# source was available?
So let's see this game in Visual Studio...
Here's a snip of the OpenRA.Game Project (to give you a feel for the amount of code we're talking about)
The CNC and RA Mod's are just about as big...
And a quick snip of the game.cs
If you've always wanted to see a complete/major game in C#, to help out on such a project or just review 1.9 bazillion lines of game code, OpenRA is standing by.