The New York Times has an article on church groups using Halo 3 at their meetings. Personally, I find this fascinating. I wonder if their game play is any different, or it's just used as "kill aliens while I talk to you about God."
The possibilities are, of course, endless. You could specifically interpret the game as some gargantuo metaphor...are the aliens demons? (hey, they actually are demons in Doom) Is the game a great recreation of the crusades?
Are there any actual explicitly Christian video games out there? Any that incorporate the level of action as the average 1st person shooter? I smell a market niche...
(incidentally, you might've seen this story if you've been reading interwub postcards, my other blog...hint, hint)