To be honest I'd rather just stick to paintball, ComSim sounds like some kind of Matrix LARP thing. I guess it'd be good if you don't have any Paintball equipment, and you want to play around in a city. But, I'd miss the shooting part too much. Hunting is fun, but thats only half the game.
http://r.vinot.free.fr/spacehulk/
QSpace Hulk, a remake of the old Games Workshop game Space Hulk, but for PC. No AI. Only hotseat and PBEM. They included network multiplay in the last version, but that feature doesn't work on XP boxes.