Here's a curiosity:

Do you know a game that was completely written in a functional programming language like Haskell or Lisp? Are there any graphical libraries for them, or anything where someone could write a game with? If there are, how advanced they are? Are there engines? OpenGL support? I've played with haskell a bit and just found it incredibly interesting, and I would like to know your opinion about the subject.

Here's something interesting that I've found: Game Oriented Assembly Lisp (or GOAL).

Another interesting link (Haskell): http://www.haskell.org/haskellwiki/Game_Development

I think John Carmack implemented Wolfenstein3D in Haskell a while ago, don't think he released the sources though. You could try to look it up in his twitter account.

I just saw his tweet now. Wolfenstein3D on Haskell? That's insane :). But coming from him, I'm not surprised with it.